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  • March 18, 2023 2:18 PM | Howard Ratsch (Administrator)

    Educational Blog

    This article represents the views of the author.  The article has not been fact checked by myself, the Board of Directors or any member of the USA Dive Club.

    Copyright Disclaimer under section 107 of the Copyright Act of 1976, allowance is made for “fair use” for purposes such as criticism, comment, news reporting, teaching, scholarship, education and research. Fair use is a use permitted by copyright statute that might otherwise be infringing.

    What defines a risk? What is involved in taking a risk?

    Difficult questions to answer, because something that feels risky to one person might be yawn-worthy to another. Risk taking, unscientifically, is something you do that gets your blood up, raises your heartbeat, awakens your senses, and makes you hyper-aware of your surroundings.

    Surely we can agree that the Covid pandemic has added an unexpected level of risk to everyday life. Add poor drivers, mass shootings, contentious politics, global climate change, and many are left believing that meeting each day is risky enough. But that’s not true for people who identify as risk-takers or thrill-seekers.

    “Everyone has a ‘risk muscle’. You keep in shape by trying new things. If you don’t, it atrophies. Make a point of using it once a day.” – Roger Von Tech

    There are many activities that go to the trouble of defining the level of risk involved with a specific activity, and while that’s not the purpose of this article, you should know that scuba diving ranks fairly high on the risky behavior scale–higher than skydiving and rappelling. And, cave/wreck diving or freediving isn’t on any risk scale we could locate. We can assume it’s up there—near or at the top.

    Please use this GUE link below for the full article by   Pat Jablonski

    Risk-Takers, Thrill-Seekers, Sensation-Seekers, and … You? - InDepth (

  • February 22, 2023 7:58 AM | Howard Ratsch (Administrator)


    By Jill Hottel

    Fish Identification and Why it's an Important Scuba Diving Skill (

    This article represents the views of the author.  The article has not been fact checked by myself, the Board of Directors or any member of the USA Dive Club.

    Copyright Disclaimer under section 107 of the Copyright Act of 1976, allowance is made for “fair use” for purposes such as criticism, comment, news reporting, teaching, scholarship, education and research. Fair use is a use permitted by copyright statute that might otherwise be infringing.


    If you surveyed 100 recreational divers about the top ten most important skills for a diver, I don’t think fish identification would garner many votes. True, finning techniques or navigation may seem more important but don’t discount fish ID – it’s my favorite skill to teach as an instructor. Here are five reasons why you should put the work in to improve your fish ID skills:

    1. Fish identification is low and slow

    In 2009 I traveled to Manzanillo, Mexico, to become a dive professional. My first instructor there taught me to look for the small stuff. Thus, I learned to dive as close to the bottom as possible without stirring it up…I had to get close to see what I was looking for. Blennies. To do this, of course, I needed to dial in my buoyancy and trim so I didn’t come crashing down onto the reef or drag my gauges across the top. Blennies are cute, odd-shaped bottom dwellers that burrow in the seafloor or inhabit crevices on the reef or rocky substrate. You can find them poking out of their hidey holes, with their mouths agape trying to communicate that you are encroaching on their territory. To me, it looks like they are talking. Perhaps shouting out, “Hey! Did you hear about what went down at the cleaning station the other day?” I like to get close to them…almost nose-to-nose…and say hi. Some species are a mere inch in length, but all of them have an outsized personality.

    Fish ID is also slow. If you power fin over the reef, you’ll miss the fish. Not only will you be going too fast to focus on them, you’ll likely startle them by disturbing the water column driving them deeper into the reef or back into their hidey holes. The slower you go the more you’ll see – you’ll be less intrusive moving through the water, and fish will be less startled by you. This also plays to your advantage if you are a photographer, because you’ll have more time to photograph your subjects.

    2. Fish ID helps you develop keen observation skills

    You don’t have to know the names of the fish to excel, you just have to make observations on their anatomy and distinctive features (i.e., shape, color, pattern) – being able to describe the fish you’ve seen will allow you to effectively describe them to someone else (like the dive guide) or enable you to look them up in your fish ID book. The more you practice, the more you’ll observe, all of which are clues to identifying the fish. What shape is the body…does it have a sloping head, kind of odd-looking, or round like a dinner plate? What stands out…does it have big, juicy lips, or is it primarily red in color? What did you observe about its behavior…is it free swimming or does it hug the bottom?

    My old logbook entries are funny because I’d make up names for the fish I’d see – such as black and tans (bicolor damselfish) or LSU fish (fairy basslet). Or I’d write a detailed description of the fish…like the “fish that lies flat and looks like sand” (peacock flounder) or “silver ones/red on back with bulging black eyes sitting in groups of 3-4 weird” (squirrelfish).

    3. There’s always something new to see, if you know where to look

    There’s a sign in Fife, Scotland, that reads, “Tak tent o sma things” – it translates to “pay attention to the small things.” That’s what I think after I take my giant stride, once I’ve arrived at depth and am beginning my dive. Keep your eyes open, and pay attention to the small things. What do I see? What is unfamiliar? Throughout my dive I keep my eyes peeled – looking under, behind and inside the reef – hoping to spot something new to me…some fish I’ve yet to identify. I never come out of the water disappointed.

    Several years ago, I met a diver at his office where he had video footage from a recent dive trip playing. Mesmerized, I asked him about his trip and the diving. Disappointedly, he said he’d never go back there again because he didn’t see anything. “No sharks, turtles. Nothing.” As Mr. T would say, “I pity the fool.”

    It’s true, most divers enjoy spotting an apex predator and singing the Jaws theme song to themselves (I’m not the only diver who does this, right?), or watching turtles glide across a reef. But to say that there was nothing to see because you didn’t see a shark or turtle is absurd. There is a seemingly endless array of small marine life to enjoy in our oceans, you just have to look for it. It helps to readjust your thinking by focusing on the abundance of the small things.

    4. Fish identification is empowering

    You know that feeling when you arrive to a party, walk in and start picking out all the people you know…you get the same feeling when you drop onto a reef and start identifying the fish residents. Not only recognizing them, but naming them. Or better yet, when you’re back on the boat and another diver asks, “what’s the name of that rainbow-colored fish I saw munching on coral and pooping,” and you come in clutch with the answer, “Oh, that sounds like a rainbow parrotfish.” It’s a great feeling to have an answer, and to be able to share your acquired knowledge with a fellow diver. What’s even more satisfying is being familiar with what you see underwater and feeling connected to it. This growing familiarity empowers a diver to want to see and learn more, encouraging them to seek out new underwater experiences.

    5. Fish ID is a lifelong pursuit 

    There are so many fish in the sea that you’ll never know them all. And even if you become an expert fish IDer in, say, the tropical Western Atlantic, you can always travel to the other side of the world and start learning the fish in the Indo-Pacific. While the classification scheme is the same across the globe, you’ll encounter different species depending on where you are. There are always new fish to see, which means you will always be on the perpetual journey of exploration.


    Fish ID is something you can work on on your own – start with a good fish resource (such as these books from New World Publications) or visit Reef Environmental Education Foundation to view their variety of learning resources dedicated to building your fish ID knowledge. You can also visit your local dive shop and sign up for SDI’s Marine Ecosystems Awareness specialty course. This course will not only cover fish ID for the local area, but also builds a diver’s understanding of marine and freshwater environments, highlights the risks they face, and identifies ways divers can contribute to their conservation.

    About the Author

    Jill Hottel (Instructor #32568) has been diving since 2000 (that’s more than half her life!). She serves as the executive director of Diving with Heroes, a nonprofit that provides disabled veterans with opportunities to scuba dive. She is passionate about fish ID, and she shares that passion with all her divers. Her favorite fish are the whale shark, yellowhead jawfish, frogfish and (of course) blennies.

  • January 23, 2023 2:00 PM | Howard Ratsch (Administrator)

    Trouble at 100 Feet | Lessons for Life

    A medical emergency underwater puts a diver in crisis.

    By Eric Douglas April 16, 2021

    This article represents the views of the author.  The article has not been fact checked by myself, the Board of Directors or any member of the USA Dive Club.

    Copyright Disclaimer under section 107 of the Copyright Act of 1976, allowance is made for “fair use” for purposes such as criticism, comment, news reporting, teaching, scholarship, education and research. Fair use is a use permitted by copyright statute that might otherwise be infringing.

    Ted was stoked to begin his training as a rebreather diver. He had been working toward this goal for several years, building up his dive experience and researching the best unit for his needs. Now he was nearing the end of his first tec closed-circuit rebreather diving course.

    He was a bit uncomfortable, struggling to catch his breath, but he chalked it up to nerves and getting used to the closed-circuit device.

    The Diver

    Ted was a 51-year-old male and an experienced, certified diver. He had reached a personal income level that allowed him to travel more. He wanted to up his dive game by learning to dive with a rebreather system. He looked forward to the extended bottom time the device provided, along with the ability to move silently through the water. As an avid underwater photographer, he hoped it would help him get closer to sea life so he could capture critters in their natural state.

    A year earlier, he had consulted a local dive instructor about what he needed to do to get rebreather certified. Since then, he had been working toward the goal, logging hours underwater and practicing his diving skills.

    The Dive

    After reviewing the techniques unique to diving a rebreather system in a pool, Ted, his dive buddy and their instructor made their way to open water for a series of checkout dives. Conditions were good on the ocean as they entered the water from a local charter boat that was accustomed to working with technical divers.

     The boat and its crew didn’t have a problem with them making long, deep dives, and everyone on board was a tec diver. Ted’s group planned the dive for 90 minutes at a max depth of 130 feet of seawater. They made their way gradually toward the final depth, descending along the reef structure.

    The Accident

    The divers had been in the water for 45 minutes, slowly making their way to their planned maximum depth. At 97 feet, Ted began struggling to breathe. He signaled that he was having trouble with his rebreather unit and indicated he needed to ascend to the surface.

    One hard and fast rule of technical diving is that any diver can call any dive for any reason.

    When Ted indicated he was having a problem, the instructor immediately agreed that they should end the dive. All three divers began ascending toward the boat. On the way, Ted lost consciousness. The group had obligatory decompression time, but they ignored it and continued toward the boat to get Ted the help he needed.

    The boat crew immediately began lifesaving procedures, but Ted could not be resuscitated.


    An after-accident analysis of Ted’s gear indicated his rebreather system was working normally. The equipment wasn’t to blame for this dive accident. Although the group omitted decompression on the way to the surface, that wasn’t the cause of this accident either. Ted’s problems began at depth. Neither of the divers with Ted exhibited any symptoms of decompression sickness because of the omitted decompression, although they did not return to the water and were observed for the rest of the day to make sure no problems arose. After performing an autopsy, the medical examiner determined that Ted had a cardiac event underwater. He had dilated cardiomyopathy, hypertensive heart disease (high blood pressure) and coronary atherosclerosis (hardening of the arteries). He was also obese and had a medical history of sleep apnea. A dilated cardiomyopathy is a weakening of the heart’s primary pumping chamber, the left ventricle. This can be caused by a variety of conditions, including coronary artery blockages, long-standing high blood pressure, diabetes mellitus and viral infections. In fact, in a large percentage of cases, doctors are unable to determine the underlying cause of the condition. Regardless of the cause, this weakening of the heart muscle can result in a multitude of problems, such as fatigue, shortness of breath and life-threatening heart-rhythm abnormalities .There is a special concern for divers with dilated cardiomyopathy. When humans are immersed in water (swimming or diving), there is a fluid shift of about 700 cubic centimeters (about 1.5 pints) from the periphery to the central circulation. In patients with dilated cardiomyopathy, this additional fluid load might not be tolerated by the heart, resulting in symptoms of severe shortness of breath from congestive heart failure. While we will never know for sure, this is probably what happened to Ted.In preparation for learning to use the rebreather system, Ted spent a lot of time diving and working on his underwater skills. He also studied the physics of mixed gases. What he didn’t focus on was the physiology of diving and preparing his body. What is important to remember is that diving, be it on open-circuit scuba or a rebreather, puts additional strain on the body. Water provides more resistance than air, so your body has to work harder to move. Your breathing is somewhat restricted, and you might need to exert yourself if, for instance, you are caught in a current and have to swim harder to get back to the boat. Additionally, having a cardiac event underwater or on a dive boat makes it much more difficcult to get to emergency medical care. At your local mall, you can expect to receive bystander care within moments. Emergency medical services will likely arrive with a full range of equipment and medicine to stabilize you before you get to the hospital, likely in less than 10 minutes.

    On a dive boat, even with the best-trained crew available, there will be delays getting you out of the water and out of your gear before care can begin. And then there are longer delays getting you to advanced medical care. We don’t know if Ted knew about his heart condition; it’s likely he did not. His doctor had diagnosed him with high blood pressure and sleep apnea, but Ted wasn’t controlling either condition well. All of that reinforces the importance of being physically fit for diving. Ted was 51 years old, but his medical history indicates that he probably should have had a conversation with his doctor about diving and what those conditions meant to his overall health. During his year of preparation for technical diving, he should have spent more time training himself physically and managing his health complications.

    There is a possibility that if Ted had been given a stress test, an echocardiogram and a complete physical, a diving physician would have told him he should consider giving up diving. While that choice might be unthinkable to some, the idea of dying on a dive boat, putting your dive buddy at risk in the process, is inarguably worse.

    Douglas Ebersole, M.D., consulted on this column. He is an interventional cardiologist at the Watson Clinic in Lakeland, Florida, and the director of the Structural Heart Program at Lakeland Regional Health Medical Center. Additionally, he is a cardiology consultant to Divers Alert Network, as well as an accomplished diver and closed-circuit rebreather instructor.

    Lessons for Life

    • Stay fit for diving. Exercise regularly, and manage your weight.
    • Taking medication does not necessarily prevent you from diving. Rather, the underlying condition the medication is intended to treat is the concern.
    • Consult a physician familiar with diving to ensure you are fit to dive, especially if you have any medical conditions thought to be a contraindication.
  • December 22, 2022 11:31 AM | Howard Ratsch (Administrator)

    Educational Blog

    A Brief HISTORY OF SCUBA’S Ubiquitous Aluminum 80 Cylinder

    By Mark Gresham and Bill High. 

    This article represents the views of the author.  The article has not been fact checked by myself, the Board of Directors or any member of the USA Dive Club.

    Copyright Disclaimer under section 107 of the Copyright Act of 1976, allowance is made for “fair use” for purposes such as criticism, comment, news reporting, teaching, scholarship, education and research. Fair use is a use permitted by copyright statute that might otherwise be infringing.

    The “80” had a down-side. At 3,000 psig/207 bar, that pressure was a bit high for most compressors in use. Many dive stores could not fill them completely. More importantly, its diameter was slightly greater than the common steel cylinder, so it would not fit into the non-adjustable backpacks.

    Alcan (Luxfer) was not the first to make an aluminum scuba cylinder. In the mid-fifties, the US Navy purchased many aluminum cylinders from Pressed Steel Tank Co. which were not Interstate Commerce Commission (ICC) approved for commercial use. Those cylinders were made by a spinning process that required a plug to close the round bottom. By the 1970s, some of those cylinders found their way into recreational diving; however, they were illegal to fill or transport.

    For several years, the Luxfer “80” was the only kid on the block. In 1981, the competitors Walter Kidde Co. and Catalina Tank Co. began making competitive cylinder models using the somewhat different alloy, 6061. 

    The bright future for the “80” continued into the 1980’s. Adjustable backpacks solved the size issue. Corrosion resistance was evident. Several colors were available. There were two things we did not know. First, in 1982 and 1983, Luxfer produced its cylinders using the 6351 alloy with a somewhat elevated trace lead content. That became an issue later. Catalina and Kidde continued using 6061 alloy. Secondly, a metallurgical issue raised its ugly head.

    For the complete GUE article, Please use the link below

    A Brief History of Scuba’s Ubiquitous Aluminum 80 Cylinder - InDepth (

  • November 22, 2022 5:30 PM | Howard Ratsch (Administrator)

    This article represents the views of the author.  The article has not been fact checked by myself, the Board of Directors or any member of the USA Dive Club.

    Copyright Disclaimer under section 107 of the Copyright Act of 1976, allowance is made for “fair use” for purposes such as criticism, comment, news reporting, teaching, scholarship, education and research. Fair use is a use permitted by copyright statute that might otherwise be infringing.

    Going Deep

    By Jon Hardy

    Setting the Stage

    Jerry was an occasional diver who made most of his dives when traveling on vacation. Being single, he usually traveled alone, but sometimes a non-diving friend joined him.

    While on an island vacation, Jerry found a dive operator offering a mid-week deep dive to an offshore rock pile that featured black coral and rare fish. Although Jerry had not been diving recently, when the dive operator asked about his dive experience, Jerry implied that he had much more experience than he actually did and signed up for the advanced dive.

    The dive plan was first to anchor the boat in the sand beside the rock pile. Next, after a thorough briefing, the divemaster would lead the six divers down the anchor line, and then put a lift bag on the anchor to make retrieval easier. The divers would then explore the site. After 10 minutes in warm, clear, calm waters, ranging in depth from 135 to 150 feet, the group would proceed up the anchor line, making a decompression stop and a safety stop, and then head back to the boat. A hang tank would be provided at 15 feet in case anyone ran low on air during the stops.

    The Dive

    The first sign of difficulty came when Jerry arrived at the dive store the morning of the dive. The divemaster for the trip discovered that Jerry needed to rent much of his gear and that he had no dive computer. Then, on the trip out, the divemaster thought that Jerry's excessive chatter about dives he had made did not ring true. But, by this time, the divemaster felt he needed to press on with the dive.

    The anchoring and briefing went as planned, although the current was stronger than the divemaster had planned for. Descending on the anchor line was a bit more work than expected, but all the divers arrived on the bottom, gave the OK sign and proceeded to explore the near side of the rock pile, which was the lee side, out of the current. Meanwhile, the divemaster set the anchor and attached the lift bag. Jerry had swum off to the deeper end of the rocks at 145 feet, but was still in view.

    After a couple of minutes, when Jerry had not returned to the group, the divemaster swam to him and found him motionless, unconscious and not breathing. The divemaster grabbed Jerry, towed him to the anchor line and started to ascend, abandoning the other five divers.

    Because the current was strong and Jerry was not breathing, the divemaster skipped the stops. As soon as they were on deck, CPR was started. Efforts to revive Jerry failed, and he was pronounced dead at a local hospital.


    What most likely befell Jerry is known as deep-water blackout, a little understood and fortunately relatively rare accident. Deep-water blackout most often occurs during dives beyond 130 feet on air, and to divers with little or no experience in the particular demands of this type of diving. Deep-water blackout may be related to fitness, narcosis, gas density, carbon dioxide retention and breathing resistance, but none of this is clearly understood.

    Lessons for Life

    • Scuba diving takes practice to keep skills fresh. Refresher and advanced courses are ideal for this.
    • Be honest with yourself and others concerning your diving experience.
    • Do not engage in deep or decompression diving unless you have the training and experience to do so. Some training agencies now offer training in extended-range diving--diving beyond the usual recreational limits.
    • If you are going to make serious or demanding dives, you should have your own high-performance regulator, instruments (including both a dive computer and a compass) and BC.
  • October 20, 2022 7:24 PM | Howard Ratsch (Administrator)

    Educational Blog

    This article represents the views of the authors.  The article has not been fact checked by myself, the Board of Directors or any member of the USA Dive Club.

    Copyright Disclaimer under section 107 of the Copyright Act of 1976, allowance is made for “fair use” for purposes such as criticism, comment, news reporting, teaching, scholarship, education and research. Fair use is a use permitted by copyright statute that might otherwise be infringing.


    Don’t Panic: Understanding the Causes and Remedies of Diver Panic

    The “Hitchhikers Guide to The Galaxy” summarized it neatly: Don’t Panic! For good reason: taken together panic/anxiety/stress have been ranked as one the top three risk factors in scuba diving incidents. Here clinical psychologist and scuba instructor Laura Walton dives into the definition and causes of panic, explains why seeking to avoid panic can make matters worse, and offers effective strategies to consider.

    A handful of studies suggest that as many as a quarter to a half of qualified (i.e. open water or higher) recreational divers have experienced panic or near-panic on at least one occasion (Colvard & Colvard, 2003; Morgan, 1995). 

    Please use this GUE link below for the full article by Laura Walton

    Don’t Panic: Understanding the Causes and Remedies of Diver Panic - InDepth (

  • September 22, 2022 6:07 PM | Howard Ratsch (Administrator)

    Sustainable Tourism and Diving: Tips for Treading Lightly - Dive Training Magazine (

    This article represents the views of the authors.  The article has not been fact checked by myself, the Board of Directors or any member of the USA Dive Club.

    Copyright Disclaimer under section 107 of the Copyright Act of 1976, allowance is made for “fair use” for purposes such as criticism, comment, news reporting, teaching, scholarship, education and research. Fair use is a use permitted by copyright statute that might otherwise be infringing.

    Sustainable Tourism and Diving: Tips for Treading Lightly

    Story by Alex Brylske
    November 20, 2019

    If you’re a diver, here’s a little tidbit I’ll wager you’re completely unaware of: Did you know you’re an “adventure tourist?” Indeed, you are — at least according to the travel industry. In fact, scuba diving and snorkeling are specifically listed as adventure travel activities by what may be the top expert in the field — the Adventure Travel Trade Association. They define an adventure tourist as anyone engaged in a travel experience that involves at least two of three elements: 1) physical activity; 2) the natural environment and 3) cultural immersion.

    But before venturing further on the adventure tourism path, let’s look first at travel and tourism in general. In terms of both direct and indirect impacts, tourism is a major contributor to the global economy. The international tourism industry generates nearly one trillion dollars annually and comprises 30 percent of the world’s exports of commercial services (six percent of total exports). According to the World Travel and Tourism Council, it accounts for more than nine percent of global Gross Domestic Product (GDP) and employs one in every 10 people on earth. By comparison only three other industries rank higher in global export: fuels, chemicals and automotive products. And it’s growing.

    The scuba diving industry is an excellent example of how tourism has grown in recent years. In fact, it has changed fundamentally. Once driven by scuba equipment sales it’s now driven by travel. For example, at 19 billion dollars in revenue annually, dive travel now accounts for more than six times the revenue generated by dive equipment sales.

    But you’re not in the diving or tourism business. So, why should you care? The reason is simple. The dollars quoted in all those statistics are your dollars. Thus, you have a very big voice in how, where and on what that money is spent. In other words, you have enormous power to influence the future direction of the travel industry, generally, and the dive travel industry, directly. More importantly, your dollars don’t just contribute to the financial success of whatever travel provider you choose. If you choose wisely, your dollars can also have a positive impact on the quality of the destination you visit and on those who live there.

    RELATED READ: How Shark Tourism is Protecting Global Shark Populations

    So, what’s the problem? Well, it turns out that tourism can be a double-edged sword. In many ways it has the potential to be a victim of its own success.

    International tourist arrivals (overnight visitors) now exceed a billion per year — millions of which are scuba divers. That’s equivalent to the entire population of China and the numbers are expected to increase to nearly two billion by 2030. So, it’s hardly surprising that at destinations where their bread and butter is a natural resource (like coral reefs), the impact from tourism can range from harmful to devastating. Yet, tourism can be done responsibly and actually become a positive force for conservation, if — and that’s a big “if” — it’s done right. It’s up to you. As one travel expert has puts it, “Tourism is like fire — it can cook your meal, or it can burn your house down. The choice is yours.” Preventing the fire of tourism from getting out of control is the biggest challenge facing the travel industry today because some popular destinations around the world are being literally “loved to death.” This phenomenon even has a name — over tourism.

    When it comes to the environmental consequences of over tourism, marine tourism is perhaps the sector most affected of all nature-based travel activities. As a major share of marine tourism takes place in the tropics — and what draws folks there is the environment — it doesn’t take a genius to realize that much of marine tourism is wholly dependent upon healthy coral reefs and associated ecosystems (seagrass beds and mangrove forests). And surely there’s no segment of tourism more dependent on the continued existence of healthy coral reefs than scuba diving.

    Of course, tourism isn’t the primary reason for the demise of earth’s coral reefs. And though factors such as destructive fishing practices, pollution, coastal development and climate change are far bigger problems, tourism does play a role. However, the reason reefs at popular dive destinations are in trouble isn’t from what you might assume. When talk turns to how coral reefs are degraded at popular tourist sites, divers are often viewed as the culprits. After all, our high visibility and close association with coral reefs makes us easy targets. Without question, anchors as well as clumsy and careless divers do take their toll on our beloved reefs. And the overabundance of divers on any reef, regardless of their behavior, will have a negative impact. But this problem pales in comparison to other destructive factors.

    A colleague of mine once summed up the problem quite accurately. “A diver,” he contends, “probably does more damage to a coral reef by flushing the toilet in his hotel room than he’ll ever do by diving on one.” It was a glib but astute insight into the real problem. From a tourism perspective, the concern is less about direct damage from recreation activities like diving and boating, and more about the indirect threats from the infrastructure needed to support tourism. Every tourist needs a place to eat, sleep and go to the bathroom. They also prefer that these facilities be very near or, ideally, on the water. In addition, every tourist demands the facilities and services that make tourism possible, such as beaches, docks and marinas. These all add to the eutrophication, pollution, demand for seafood and sedimentation problems already threatening reefs from local population pressure (a population pressure that’s sometimes driven by tourism). And considering that on small islands, tourists can sometimes outnumber the local residents, it’s easy to understand the validity of my friend’s “flushing the toilet” assertion.

    While the environmental consequences of tourism are often obvious — at least for those willing to take a closer look — there are other not-so-obvious results that involve people. Clearly, the consequences of a rapidly expanding tourism industry have, at many destinations, been as detrimental to societies as it has to the physical environment. For instance, many developing countries’ job opportunities in tourism have encouraged the migration of people to tourism centers, often disrupting or outright destroying traditional ways of life. Already some communities and cultures have been completely displaced or destroyed by a booming tourism trade. This social upheaval can lead to problems with crime, pollution and a general erosion in the fabric of society. Ironically, this can lead to the decline in the appeal of a destination because it no longer feels “authentic” to travelers, thus killing the golden egg-bearing goose.

    RELATED READ: A Guide to Ocean Conservation Organizations and Efforts

    This phenomenon is, in fact, so common and well-studied that it even has a name — the Tourism Area Life Cycle (TALC). The TALC cycle views tourism as a dynamic process where destinations go through predictable successive stages. It starts when a relatively undeveloped location initially attracts a few adventurous tourists seeking pristine nature and indigenous cultures. Then, as tour operators and related businesses recognize the market potential of the location, the local tourism industry rapidly expands and develops. However, the changed nature of the now “discovered” destination causes the type of tourists who were initially attracted by the undeveloped nature of the location to move on to other destinations that remain undeveloped and pristine — and the cycle is repeated.

    But there’s nothing inevitable about this cycle. By recognizing the cycle of over tourism and unsustainable tourism practice soon enough, destinations can reverse the downward spiral. Corrective actions can be taken, such as limiting tourist numbers, establishing marine protected areas, improving infrastructure codes or restricting certain destructive practices. Ideally, the entire tourism paradigm can change, but this calls for a different kind of tourism: Sustainable tourism.

    Sustainable Tourism: A New Paradigm

    The problem is that undiscovered tourism destinations are not unlimited. As a popular protest poster tells us, “There is No Planet B.” Tourism has become so big that we have almost run out of truly pristine locations. So, without the option of creating more places on earth, the only reasonable alternative is conducting the business of tourism in a different way — and that’s exactly what’s beginning to happen all around the world. Tourism, and tourists, are changing for the better. So, let’s look at how.

    Traditionally, the reason for travel has been to rest and relax. In the marine sector, this emphasis on leisure is referred to as “sun, sea and sand” tourism. This describes the bulk of marine tourists and probably always will. But over the past few decades there have been some significant changes. Increasingly, tourists want more from their holiday than a suntan and souvenirs. These more intrepid travelers — I’ll no longer call them tourists — want a closer and more experiential encounter with the destination they visit than lying on the beach during the day and partying at night. For many, the primary motivation for selecting a destination is not the quality of its beaches, golf courses or of night life, but its healthy natural environment and undisturbed culture. In the words of one tourism expert, “An increasing number of travelers today want holiday experiences that are authentic, immersive and self-directed.” And what’s good news for us is that’s almost the perfect definition of scuba diving.

    The other good news is that, while the travel and tourism industry is sustaining a healthy grow of five to seven percent annually, the adventure and nature-based travel industries are growing in the 20 to 30 percent range. And even more significantly, these travelers most often understand, in fact prefer, to travel responsibly. Of course, this hasn’t gone unnoticed by many within the travel industry and has already led to massive changes in the travel products offered by many destinations and how they’re marketed.

    The evolution of adventure travel can be traced to early attempts to meet the demand of changing attitudes toward tourism, which led to the development of the ecotourism industry. From this evolved the idea that travel should not only serve the tourist but the destination and its inhabitants as well. As ecotourism became more mainstream, newer and more authentic directions were explored and the market segmented into many more specialized sectors and activities. Then, with the growing recognition of the declining state of earth’s environment, many in tourism began to realize that making tourism more accountable to both the local environment and residents could no longer be just a specialized endeavor targeted to “tree-huggers.” All forms of tourism should become part of the solution and not part of the problem. From this movement was born the idea of “responsible tourism,” or what’s become better known as “sustainable tourism” — an off-shoot of the growing concern for sustainable development.


    But what exactly does sustainable tourism really mean? While arguments rage among the experts in the field, one of the best functional definitions has been offered by those who have been involved in international tourism since its inception, Caribbean islanders. According to the Organization of Eastern Caribbean States, sustainable tourism is defined as “the optimal use of natural and cultural resources for national development on an equitable and self-sustaining basis to provide a unique visitor experience and an improved quality of life through partnership among government, the private sector and communities.” Importantly, this definition recognizes that tourism isn’t just an economic activity. As it has both environment and cultural consequences, so too must it take into account, and be responsible for, its effects. This ethos is exemplified in the commonly used sustainable tourism mantra “people, planet, profit” or what some have termed the “triple bottom line.”

    In general, sustainable tourism has six underlying goals. These include: minimizing environmental impacts; improving local contribution to sustainable development; protecting the quality of the environment by maintaining biological diversity and ecosystem function; minimizing the use of non-renewable resources; ensuring cultural integrity, local ownership and social cohesion of the community; and last, but certainly not least, providing a high quality experience for tourists.

    Today, savvy tourism operators trying to cater to the new, more environmentally and socially conscious traveler have a daunting task. No longer can they be satisfied by having the nicest hotel and restaurant or best beach or even the most exciting tours. Study after study has shown that many travelers today — a majority of European and a fast-growing number from the U.S. — are just as or more concerned with the environmental and social footprint of their travel provider as they are with the actual product. So, travel providers and destinations today aren’t turning to sustainability because it’s a nice thing to do for the earth or future generations. They’re doing so because it makes business sense and realize that not to do so will at some point will mean they’ll no longer be in business.

    So, What Can You Do?

    My experience has been that divers are a special breed. The most serious among us are anything but tourists — we’re travelers. We take very seriously our responsibility to protect the environments we visit and are increasingly recognizing that our travel demands are sometimes placing undue stress on local ecosystems and cultures. So, what we can do to help ensure that operators and destinations hear our wishes loud and clear to make tourism more sustainable is simple. As I indicated at the beginning, we can vote with our wallets. When making your choice of what destination and operator to patronize, take a few minutes to consider not only what you might “get for your dollar,” but how that destination or operator does business and reward those who are doing it right. In that way, you can become part of the solution and help drive a process that will make tourism a positive force for change. Let’s use the fire that we helped ignite to create a warm glow — not burn our house down.

  • August 22, 2022 3:02 PM | Howard Ratsch (Administrator)

    Educational Blog

    More Than Darkness: Human Factors and the Night Diver - Scuba Diving News, Gear, Education | Dive Training Magazine (

    This article represents the views of the author.  The article has not been fact checked by myself, the Board of Directors or any member of the USA Dive Club.

    Copyright Disclaimer under section 107 of the Copyright Act of 1976, allowance is made for “fair use” for purposes such as criticism, comment, news reporting, teaching, scholarship, education and research. Fair use is a use permitted by copyright statute that might otherwise be infringing.

    More Than Darkness: Human Factors and the Night Diver

    By Robert N. Rossier

    It’s like taking a stroll downtown at night,” said our instructor, Don. “Everybody is out — a really wild time.” Waving his arms in animated motion, he proceeds to describe the reef-city after dark. “You’ve got corals and tubeworms dancing to the tune of the tides, tentacles swaying in the gentle current. A parrotfish is curled up on the corner in its translucent sack, trying to sleep it off, while gangs of crustaceans cruise the dark corners of the reef’s back streets. And the city lights are a thing of beauty — a soft glow of bioluminescent algae and comb jellies. But like taking a stroll through the city at night,” he warns, “you’ve got to be careful, take precautions. After all, it’s a different world down there at night.”

    When you first hear about night diving, that’s the focus — the difference in the marine life at night. But how about us, the divers? Are we different, too? At first blush, night diving might not seem like such a big deal. It’s dark, so we use dive lights. No problem, right? But nothing is that simple in diving.

    In reality, some very important differences distinguish day from night diving. Diving at night introduces an entirely new regime of human factors considerations that affect our physiological, psychological and biomechanical adaptation to the underwater environment. By understanding these human factors considerations, we can improve our aquatic decision-making and safety in the water after dark.

    Aquatic Decision Making

    At the core of our ability to dive safely is our judgment and decision-making ability. To exercise good judgment and make safe aquatic decisions requires a continuous assessment of three vital factors: the environment, our equipment, and our own abilities and limits. Training and experience are key elements in making these assessments, but our experience and training in daytime diving does not necessarily prepare us for a night excursion under the waves. Each of these factors takes on new dimensions as daylight fades and shadows grow longer. Water conditions and diving environments considered within our abilities for a day dive become much more difficult to negotiate at night. Our familiarity with our equipment becomes more critical when diving in darkness, and additional equipment is needed to ensure proper vision, communication and navigation, both underwater and on the surface. Finally, our own abilities and limits vary much like the daily cycles of day and night.

    The Rhythm of the Night

    One of the first implications in night diving is the effect of our circadian rhythms, our daily sleep-wake cycles that alter our states of consciousness. Body temperatures, blood pressure, stress hormones, digestive secretions and mental alertness all follow a daily pattern that resets itself according to daily cycles of sunlight and darkness. Of these, mental alertness may well be the most important to a diver, as it affects our decision-making ability.

    According to experts in the field of circadian science, a person rising at 7:30 a.m. with adequate sleep will experience peak alertness levels in the morning around 8 to 9, and again in the evening between 7 and 9. (See Figure 1.) Alertness drops to a lower level from about 12 noon to 3 p.m. and drops off rapidly after 9 p.m. Based on this data, divers can generally expect reduced mental alertness on a night dive. The excitement of a night dive might conspire to artificially elevate mental alertness, but other factors, including acute and chronic fatigue, may also come into play.

    The effects of fatigue on human performance have long been known and understood. Acute or short-term fatigue is the tiredness experienced after long periods of physical or mental strain. Work, study, travel, lack of sleep and physical exercise can induce episodes of acute fatigue. The symptoms include reduced coordination and impaired alertness, both of which can be problems for divers. If a diver works, plays or parties too hard over a period of several days, the effects of acute fatigue can significantly degrade his or her performance and safety on a dive.

    To illustrate the importance of mental alertness, consider the fact that 32 percent of marine accidents occur between the hours of 4 a.m. and 8 a.m. It’s also interesting to note that four of the worst industrial accidents in recent history involved impaired judgment caused by fatigue. The Chernobyl and Three Mile Island nuclear power plant accidents, the grounding of the Exxon Valdez off the coast of Alaska and the Bhopal, India, chemical plant leak all occurred between midnight and 5 a.m. — a period when mental alertness is at its lowest.

    One approach to minimizing the effects of reduced mental alertness is to carefully plan and prepare for night dives. By making night dives relatively simple and conducting them in low-risk environments, we can also reduce the potential for problems.

    Circadian rhythms and fatigue aren’t the only human factors challenges faced by night divers. Night diving also presents a number of physiological and biomechanical considerations, including nutrition, night vision adaptation, heat balance and increased task loading.

    Nutrition: A Diet for Night Diving

    Nutrition is an important consideration for divers regardless of when they dive, but nutritional strategy is particularly important at night, when we strive to overcome the effects of circadian rhythms and fatigue. Scientists and nutritionists have learned that good nutrition and eating habits play an important role in mental performance. The types of foods eaten and the sequence in which they are consumed have a marked impact on our state of mind, mental alertness and reflexes.

    Chemical neurotransmitters derived from the foods we eat help transmit messages to the brain, causing a response in terms of mental acuity and activity. Seratonin, a chemical neurotransmitter derived from carbohydrates, tends to have a calming, relaxing effect on mental activity. While this can help reduce stress, too much of a good thing can be bad. A high-carbohydrate meal consisting of pasta, crepes, potatoes, starchy vegetables and sweets can increase seratonin levels enough to induce not just a pleasant feeling, but lethargy and the need to sleep. Likewise, fats tend to prolong digestion and rob the brain of blood to aid in the digestion process. The result is fatigue, sleepiness and overall lack of alertness.

    Alternatively, a meal that begins with high-protein foods, such as steak, eggs and high-protein cereals and is relatively low in carbohydrates and fat, will help promote mental alertness. Dopamine and norepinephrine, derived from protein in our food, stimulate the brain to higher levels of alertness and activity.

    Most divers are savvy enough to avoid alcohol prior to a night dive. Alcohol affects both the central nervous system and the circulatory system in ways that can erode the margin of safety when diving. Even a small amount of alcohol can degrade mental acuity, increase heat loss and predispose a diver to decompression illness. (See sidebar.) When planning a dive after dark, it’s best to stay away from the bar.

    Night Vision Adaptation: Seeing Isn’t Always Believing

    As most divers would agree, the most obvious difference between a day dive and night dive is our inability to see as well at night. Ambient lighting in daylight allows us to see clearly, and our peripheral vision is limited only by the physical constraints of our mask. At night, our vision is limited by the beam of our dive light. This tends to focus our attention on a relatively small area of the submarine world, but it has other consequences as well.

    Surprisingly, we can often see significantly more than we might expect even without the aid of a dive light, although vision at night without artificial light may not be quite so clear. The retina of the human eye has two types of receptors, referred to as cones and rods. The cones are located in the central area of the retina and provide clear, focused vision in well-lighted conditions. The rods, located in the area surrounding the cones, see less clearly, but more readily adapt to dark lighting conditions. “For more information, see “Understanding and Equipping for Underwater Vision” in the June 2000 issue.”

    Our best night vision develops after a period of exposure to low lighting, a process called dark adaptation. This can take as long as 30 minutes for total adaptation to blackness, but 20 minutes in dim red lighting will provide a moderate degree of adaptation. Dark adaptation is impaired by the carbon monoxide present in cigarette smoke, or a dive boat or compressor exhaust.

    Even a brief exposure to white lights will require a lengthy adaptation process to restore night vision, so be careful not to shine a dive light in another diver’s eyes. Night vision may also be impaired for some time after submerging from a brightly lit environment.

    Reduced visual perception can manifest additional problems on a night dive. Pilots have long been taught that various visual illusions, disorientation and vertigo can occur in a darkened environment. The sense of balance and motion is derived from several sources, including visual references and the intricate mechanisms of the inner ear. Normally, the brain compares inputs from various senses to determine orientation and movement.

    Without all the necessary information, the brain can become confused, causing the individual to take inappropriate actions. For example, certain accelerations caused by rapid head movement, turbulence or changes in aircraft orientation combined with limited visual references can induce spatial disorientation or vertigo in pilots. If unaware of the problem, a pilot might put his aircraft in a dangerous position while attempting to rectify an incorrectly perceived problem. In these situations, pilots must rely on the aircraft instruments to determine the orientation and true motion of the aircraft. A failure to rely on or properly interpret flight instruments combined with the lack of visual references can cause a pilot to fly a perfectly good airplane into the ground.

    For divers, a lack of visual references combined with rapid head movements, currents or surge can also create false perceptions of motion and orientation. Head-first descents in dark or limited-visibility water, even with a dive light, can result in disorientation and vertigo. (See sidebar.) When the beam of our dive light is scattered or reflected during a rapid descent, the effect can be similar to driving at night in a blinding snowstorm, and disorientation and vertigo can result. To reduce the effect, make a slow, controlled, feet-first descent when diving from a boat or in open water. Following a descent line or anchor line and monitoring a depth gauge or computer during the descent virtually eliminates the vertigo and disorientation.

    Perhaps more importantly, a lack of visual references on the ascent can lead to disorientation and excessive ascent rates. Again, avoiding this problem on a night dive is relatively simple. On a shore dive, we can maintain contact with the bottom throughout a gradual, controlled ascent. When diving from a boat or surfacing in open water, a good option is to use an ascent line and closely monitor the depth gauge or dive computer to maintain a proper ascent rate.

    What’s Hot and Who’s Not

    While the water temperature might in fact be the same day or night, several factors tend to increase our heat loss on a night dive. The air temperature is likely to be lower at night than during the day, possibly leading to greater heat loss prior to and following a night dive. In addition, we have no sun to warm us before, between and after night dives.

    It’s not unusual to begin a night dive with a heat deficit from the day’s diving, particularly if we haven’t taken the time to get the proper rest, warmth and nutrition following the day’s diving. Experts warn us that it is quite possible to “feel” warm, even if our core temperature is reduced.

    In his book Deeper into Diving, author and lecturer John Lippmann states, “Divers often disregard cumulative effects of repetitive diving. After the initial dive, the diver might experience superficial skin warming and thus feel warmer. However, his core temperature may still be reduced. Feeling warm is no guarantee that your heat losses have been replaced. The best way to show that your heat losses have been replaced is to start sweating. This shows the body needs to lose heat.”

    Don’t make the mistake of considering heat loss merely a matter of comfort. As with nutrition and fatigue, body temperature has a direct effect on mental processes. If body temperature decreases significantly, judgment might be jeopardized. In addition, breathing rate may increase in response to cold, causing a diver to consume air reserves more quickly.

    “Cold-induced mental changes are probably the danger to the diver,” writes Lippmann, “because once the brain does not work properly, wrong decisions can easily be made. Some authorities believe that long, slow cooling of the body does not stimulate shivering and the subsequent heat regeneration. As a result, the diver might not notice the heat drain from his body until significant hypothermia has developed and shivering finally occurs. Some consider this ‘silent hypothermia’ to be the major hazard to the diver in cold water, as it will make the diver more accident-prone without him being aware of it.”

    The take-home message for night divers is to minimize heat loss. Precautions against heat loss may include wearing extra exposure protection on all dives prior to a night dive, even in warm waters. We can limit our cold exposure prior to night dives by limiting bottom time and depth. Limiting bottom time reduces the period during which the heat loss is high, and limiting depth minimizes the compression of the exposure suit, thus improving its performance. Changing into warm, dry clothing between dives can reduce evaporative cooling.

    Task Loading and the One-Handed Diver

    Beyond the physiological considerations of a night dive, we must also contend with a basic biomechanical handicap. The simple act of using a hand-held dive light means that we have only one free hand. Buoyancy control, ear clearing and communications must be accomplished “single-handed.” While not necessarily a problem, the difficulty can increase dramatically when towing a surface float or manipulating other accessory equipment.

    The single-hand limitation can become a significant handicap, even when contending with relatively minor equipment problems. As Dr. Glen Egstrom, Professor Emeritus UCLA Department of Physiological Sciences, explains, “We typically use one hand to hold the dive light, and this becomes a problem in an emergency situation. If we drop the light so we can deal with the problem two-handed, we can no longer see.”


    Choosing a dive light with the proper characteristics can help solve the problem. The proper buoyancy, size and handle design may make a dive light easier to use, and thus ease the task loading associated with a night dive. Some divers find that a wrist-mounted or head-mounted light reduces the workload and makes night diving easier. Another way to cope with the problem of increased task loading during a night dive is to closely coordinate tasks with your buddy.

    The Psychology of Night Diving

    Divers are drawn to night diving like moths to a porch light, and there’s really little surprise. Just the thought of venturing into the water at night can make your skin tingle with excitement. Entering a world illuminated only by a dive light, our attention is drawn to a sharp point of focus, and we find ourselves seeing the underwater world as if for the first time. “We have an entirely different psychological set at night,” notes Egstrom. “First, there’s a peripheral narrowing that occurs as we increase the psychological stress. It becomes a more introverted dive, and this is actually something that people enjoy. The dive takes up more of our cognitive energy.”

    Indeed, there are stresses associated with a night dive. Perhaps the most obvious is the psychological stress of facing the unknown, and this can last from the planning phase throughout the entire dive. If we’re unfamiliar with the area, night diving procedures or the nature of marine life that might be encountered, our stress levels are certain to be heightened. Add unfamiliar equipment, a new or different buddy, or any other factors, and our baseline stress for a night dive can be significant.

    While a low level of stress when diving can be helpful in focusing our attention on the situation at hand, too much stress can spell trouble. As stress increases further, our ability to maintain situational awareness decreases, degrading our ability to make the assessments necessary for safe, competent decision making. Increased stress may also translate to increased breathing rate, making air reserves a more critical consideration.

    A number of situations that bump up our stress level quite abruptly can arise on night dives, especially if we’re unprepared. One of the thrills of night diving is having unexpected sea creatures suddenly loom out of the darkness. But sometimes this surprise factor creates a momentary heightening of anxiety and stress. A minor equipment problem or disorientation can also spike the stress level until the situation is resolved.

    The flip side to the enjoyable, introverted dive is a reduced situational awareness that erodes our decision-making ability. As Egstrom explains, “Since the peripheral visual field contracts during periods of increased stress, we lose a lot of information we might otherwise have.” Sometimes divers become so engrossed with their surroundings at night that they fail to closely monitor their depth or air consumption.

    The real problem comes when a situation begins to run awry. “At night, we might not be as likely to see a problem developing,” suggests Egstrom. “So this narrowing of focus can be a problem when it comes to our buddy.” If a situation is left unchecked, a full-blown emergency can develop, throwing divers into a dangerous spiral that runs out of control. An emergency that arises during the course of a night dive can elevate stress beyond the levels expected for a similar scenario in daylight. For example, a low-air or out-of-air situation may be more stressful at night due to the difficulty of resolving the problem in darkness. The net result may be an inability to successfully complete the necessary task.

    For this reason, divers must focus on situational awareness and keep tabs on their buddy during a night dive. By staying in a fixed position relative to one another, divers are less apt to become separated and can communicate more readily. By following such a protocol, the stresses that might develop can be minimized, and the potential for problems is greatly diminished.

    Training and Fitness

    The real keys to safe and enjoyable night diving are training and fitness. Proper training in night diving skills and procedures, combined with a regular program of fitness, form perhaps the best strategy for mitigating any negative human factors considerations associated with night diving.

    Night diver training focuses sharply on the night environment, skills, and the planning and preparation needed to safely conduct a night dive. All these topics are covered in a night diving specialty course. The more we know about night diving and the environment in which we’re diving, the more confidence we have in our abilities to dive safely. This confidence helps shield us against the effects of psychological stress.

    Proper planning and preparation go a long way toward avoiding disorientation, vertigo and potential emergencies. Start by preparing a detailed emergency procedures plan and review the elements of this plan before entering the water. The emergency plan should consider such contingencies as low air, out of air, entanglement, missing buddy, disorientation, failed dive light(s) and other typical equipment problems.

    To compensate for reduced mental alertness and the obvious difficulties of working in darkness, our strategy should be to prepare as much of our gear as practical during daylight hours, when our mind is alert and it’s easier to spot problems. This leaves only the process of suiting up and completing the necessary checks and safety briefings to be done prior to entering the water.

    When an unplanned situation arises on a night dive, our response should be to stop, relax, breathe normally and follow the established procedures developed as part of the predive planning. If the situation lies beyond the established emergency plan, we must think rationally and communicate before launching into an action that might be unsafe.

    A critical aspect of night diver training is practicing the requisite emergency skills and drills in a darkened environment. The need and use of dive light, and the potential need to resolve a problem in near total darkness, often adds greater complexity to underwater emergency management and requires additional practice to master.

    Handling a night diving emergency on the surface can be nearly as difficult as in the water. Hillary Viders is an international expert in emergency dive accident management who teaches Emergency Oxygen Administration and Dive Accident Management programs for the scuba, rescue and law enforcement industries. “When I teach professional rescuers,” explains Viders, “I conduct a timed drill in which each team of four people has to assemble a complete oxygen kit from a pile of assorted components while administering CPR on an ‘unconscious’ victim. Usually a professional team (one that handles oxygen equipment and performs these tasks several times every day) can complete the drill in under 60 seconds. However, when I ask the same team to repeat the identical drill in a completely darkened room, it usually takes the best group at least five times longer, and some teams cannot do it correctly at all!”

    Viders’ experience underscores the need for thorough training and preparation in all aspects of night diving. Not only must in-water skills be practiced in the dark, but skills required to effectively manage a diving emergency must also be practiced under cover of darkness.

    Good physical conditioning reduces the effort required to complete a dive, thus reducing the psychological stress. A high degree of fitness also allows us to perform better and for sustained periods when problems arise and during an emergency.

    The Bottom Line

    There’s nothing like taking that stroll down through the reef-city at night. But just like taking an evening stroll through our land-based cities, we need to be wary and take the necessary precautions. With thorough training and preparation, we can overcome most of the human factors problems and safely enter a spectacular underwater world almost beyond imagination. “It’s magic,” says Don. “Just magic.”

    The Effects of Alcohol on Divers

    All divers should know that diving and alcohol simply don’t mix.  Consumption of alcohol has the following effects on divers.

    1.     Alcohol adversely affects the central nervous system. Studies have shown that as little as 1 ounce of liquor, one bottle of beer or 4 ounces of wine can degrade motor skills and impair judgment, and will be evident in the breath and blood for a period of at least three hours. There is evidence that alcohol also impairs sleep, leaving us less rested after a night’s sleep. Fatigue reduces mental alertness and decision-making ability long after the direct effects of alcohol subside.

    2.     Alcohol alters the diver’s circulation. Alcohol tends to increase circulation to the surface of the skin while reducing circulation to the tissues. The result is an increase in heat loss, as well as an increased predisposition to DCS.

    3.     Alcohol is a diuretic and tends to dehydrate a diver. Dehydration reduces the blood’s capacity to off-gas nitrogen, since blood flow is reduced throughout the tissues, thus increasing the risk of DCS.

    4.     Alcohol alters the blood chemistry, which may increase the growth of microbubbles, thus leading to DCS. Researchers also have found that drinking increases oxygen consumption in the heart and other muscles during periods of exercise, so drinking may actually increase air consumption.


    Avoiding Vertigo and Disorientation at Night

    Vertigo is a condition in which a diver perceives motion but is unable to determine the direction or speed of movement. Vertigo can cause disorientation, dizziness and even nausea. A number of factors can induce vertigo in a diver. Cold water entering the external ear canal can induce a condition of imbalance leading to vertigo. The condition may last until the diver’s body has warmed the water. Pressure imbalances between the left and right ear during descent can also cause vertigo. Disorientation and vertigo can occur at night, when a diver has no visual references to determine orientation or motion.

    Divers can often overcome the effects of disorientation and vertigo by following standard procedures at the onset of the condition. As with all problems and potential emergencies that arise underwater, divers must remember to stop, breathe, think, then act. When disorientation occurs, refer to your compass and depth gauge to reorient yourself. Holding onto one’s self or buddy until the vertigo passes can also be helpful. Remember, too, that bubbles go up. Shine your dive light to illuminate your bubbles as an additional reference. If you can’t see your bubbles, put your hand near your regulator exhaust and feel their direction of movement.

    Effects of Low Body Core Temperature/Hypothermia

    98.6˚F (37˚C)
    Normal temperature

    95 – 98.6˚F (35 – 37˚C)
    Sensation of cold, increased heart rate, shivering, vasoconstriction, slight incoordination in hand movements, urge to urinate.

    90 – 95˚F (32.2 – 35˚C)
    Increased muscular incoordination, slurred speech, decreased or loss of shivering, weakness, apathy, drowsiness, confusion, impairment of rational thought.

    85 – 90˚F (29.4 – 32.2˚C)
    Loss of shivering, confusion progressing to coma, inability to follow commands, inappropriate behavior, loss of vision, temporary amnesia may occur, cardiac irregularities may develop.

    Night Diving Planning and Precautions

    Night diving isn’t unduly complicated, but it does require a modicum of training beyond basic open-water diving. Before attempting a night dive, be certain to receive the proper training. The following planning tips and precautions can help make your night diving safer and more enjoyable.

    1.  Always evaluate a dive site in daylight before attempting a night dive. The evaluation should include, but not be limited to: safe entry and exit locations, potential hazards (including entanglements), currents, navigation features and forecast weather conditions. Familiarity with the dive site reduces the psychological stress of a night dive, allowing divers to better focus on other safety concerns throughout the dive. Consider planning a dusk-to-night dive; enter the water while there’s still some light out, and you can gradually adjust to increasing darkness underwater.

    2.  Avoid night diving in conditions of foul weather (including forecast fog or heavy rain), high seas, strong surf, strong currents or unreasonable entanglement hazards. Such conditions pose an unnecessary risk to diver safety. Also, avoid overhead environments, including kelp, at night until you accumulate the requisite experience to do so safely.

    3.  Enjoy a good meal prior to a night dive, but avoid consumption of alcohol.

    4.  Don’t dive unless you’re well-rested and warm. If necessary, limit your daytime diving in order to be better prepared for a night diving excursion. An afternoon nap, even if it’s only 15 to 20 minutes long, may leave you feeling more rested and improve your alertness for a night dive. Mild exercise can help restore the heat deficit from daytime diving.

    5.  Proper site preparation is key to all night dives. Surface navigation lights, working lights, emergency first aid equipment, communication equipment and rescue gear should all be properly set up prior to entering the water. Always have at least one person remaining at the surface or on the boat to deal with problems such as failed surface navigation lights and dragging anchors. This individual should also be prepared to deal with emergencies and call for assistance if necessary.

    6.  Always begin a night dive with at least two dive lights per diver. If a dive light fails, the dive can be safely completed and terminated with the extra light. For hands-free night diving, consider using a wrist-mounted or head-mounted dive light as a primary dive light.

    7.  While night diving emergencies are part of every night dive plan, few divers actually practice emergency procedures at night. To keep your skills sharp, confidence high and stress reduced, practice night diving emergency skills regularly. Many skills can be accomplished in a pool, and others can be practiced safely in open water. If you haven’t practiced night emergency skills in the open water lately, have an instructor guide you through the proper exercises.

  • July 22, 2022 5:52 PM | Howard Ratsch (Administrator)

    Educational Blog

    What is Decompression Diving?, Deco Diving Tips | Scuba Diving

    This article represents the views of the author.  The article has not been fact checked by myself, the Board of Directors or any member of the USA Dive Club.

    Copyright Disclaimer under section 107 of the Copyright Act of 1976, allowance is made for “fair use” for purposes such as criticism, comment, news reporting, teaching, scholarship, education and research. Fair use is a use permitted by copyright statute that might otherwise be infringing.

    What is Decompression Diving?

    Here's what you need to know about deco dives.

    By Karl Shreeves September 2, 2021

    Decompression diving is when a diver is required to make one or more stops during their ascent to give their body time to safely release the nitrogen (or other gas, such as helium) that dissolved into their tissues during the dive.

    The pressure you’re under as you descend through water causes nitrogen to dissolve into your body tissues. The deeper the dive, the more quickly gas dissolves into your tissues. When you ascend, nitrogen dissolves from your tissues into your lungs and leaves the body through normal breathing. This is known as offgassing. If the amount of dissolved gas is within certain limits, you can ascend to the surface without any required stops – though a safety stop is standard recommended practice. This is called "no stop" or "no decompression" diving. Standard recreational diving is always planned as no stop diving, but you make a safety stop — hanging out at 15 feet for 3 to 5 minutes — as a conservative practice to further reduce risk.

    Want to do decompression diving? Start your adventure today with PADI's Tec 40 or Tec 40 Closed Circuit Rebreather courses!

    If you exceed the no stop time limits given by your dive computer, you move into "decompression dive" territory. This means you can't swim directly to the surface without unreasonable risk of getting the bends. You now have to instead ascend in stages, making progressively shallower and longer stops to give dissolved gas time to leave your tissues.

    In recreational diving, a dive with a required decompression stop is considered an emergency situation caused by accidentally exceeding a no stop limit, or being forced to do so by circumstances (which should be very rare). In commercial, tec, scientific and military diving, however, dives with required decompression may be planned. This type of diving requires additional training and specialized gear.

    Decompression Diving FAQs:

    What is deco diving used for?
    Decompression diving is appropriate when there's no other way to reasonably accomplish the dive. This is most commonly due to depth because no stop time limits become very short below 100 feet. Shallow dives can require a decompression when they are long, however. A two-hour cave exploration dive may not exceed 60 to 100 feet, but the dive is well beyond the no stop limits. Commercial divers may also make a shallow decompression dive simply because logistically it is more time and cost effective to do a single deco dive to carry out a task than to make multiple no stop dives.

    How deep can you dive without decompression?
    Practically speaking, you can make no stop dives to 130 feet. While you can, in theory, go deeper than that and stay within no stop limits, the no stop times are so short that "well within" limits is essentially impossible.

    Are diving decompression tables the same as recreational dive tables?
    Decompression dive tables differ from recreational dive tables because they list times, depths, durations and required stops well beyond the exposures recreational divers experience. While commercial and military divers often use tables, tec divers primarily use dive computers for planning and executing decompression dives.

    How do you calculate decompression stops when planning a decompression dive?

    Depending upon the depth, duration and equipment used, planning a decompression dive may take only a bit longer than a recreational dive, or may take hours over several days as the team considers and investigates alternatives and options.

    In tec diving and much scientific diving, planning decompression dives is typically done using software and/or a dive computer. Decompression dives typically involve different mixes of breathing gases, which are selected based on the dive depth and duration. To best consider all these variables, today computers are used to determine and plan the best gases and the dive schedule, plus emergency alternatives to handle reasonably possible problem situations.

    Trimix (helium/nitrogen/oxygen) is used on deeper dives to reduce gas narcosis to acceptable levels. Enriched air nitrox and pure oxygen are used during decompression because they accelerate how fast dissolved gas leaves the body. The diver switches between these during ascent, or, when using a closed circuit rebreather, changes the gas ratios during ascent. Each gas mix has a limit on how deep and how shallow it can be breathed safely, and decompression time increases disproportionately with depth, so that for dives deeper than 200 feet, often decompression is longer than the time spent at depth. The dive plan must therefore include how much of each gas is needed, where and when it's used, backup gas and equipment for emergencies, and how much of all this the diver can reasonably manage.

    What happens if you don’t decompress when scuba diving?

    If you exceed a no stop limit and surface without making the required stop or stops, your risk of decompression sickness is considered unacceptably high. How high? It depends. Any dive has some risk of decompression sickness because people vary in their physiologies and susceptibility. No computer or table can guarantee decompression sickness will never occur, even within its limits.

    What’s a good deco dive computer?
    Choose a dive computer intended for technical decompression diving. It should be capable of using several different gas mixes on the same dive. Fortunately, these are not difficult to find – ask you PADI Instructor and
    PADI Dive Center or Resort for guidance.

    An important point is that you need not one, but two compatible dive computers for this type of diving. While dive computers are highly reliable, you would not want to be stuck without your decompression info if there were a malfunction, so standard practice is to dive with two, staying within the limits of the most conservative (even identical computers will vary slightly throughout a dive).

    What should I do if my dive computer says “deco,” but I didn’t mean to do a decompression dive? What should I do if I miss the stop?
    Assuming this happens by accident on a no stop recreational dive, ascend to 15 feet (or deeper if specified by your computer) and stay there until it "clears," meaning you have stayed the required stop time. Most computers show you the time as it counts down. For a recreational "oops" situation, the time would typically be short with only one stop required. However, you may be low on gas, so do not run out of gas underwater. Stay as long as you can, but if you don't have enough air to do the stop (or you miss it altogether), surface with enough air to ascend at a proper rate and exit the water. Then stay calm, alert the divemaster and your buddy, breathe oxygen if available and monitor yourself for
    DCS signs and symptoms. Do not dive for at least 24 hours or as specified by your computer. If you have or suspect DCS, contact the Divers Alert Network and emergency medical care.

    How can I learn decompression diving?
    You can start into tec diving with either PADI’s Tec 40 course (open-circuit tec diving) or the PADI Tec 40 Closed Circuit Rebreather Diver course. These courses begin the transition from recreational diving to technical diving, which includes planning and making tec dives. After completing these, you continue into the Tec 45Tec 50, and Tec 65 courses, in which train you to make deeper, multi-stop decompression dives.

  • June 23, 2022 9:12 AM | Howard Ratsch (Administrator)

    How You Can Prevent Diving Emergencies | Scuba Diving

    This article represents the views of the author.  The article has not been fact checked by myself, the Board of Directors or any member of the USA Dive Club.

    Copyright Disclaimer under section 107 of the Copyright Act of 1976, allowance is made for “fair use” for purposes such as criticism, comment, news reporting, teaching, scholarship, education and research. Fair use is a use permitted by copyright statute that might otherwise be infringing.

    How You Can Prevent Diving Emergencies

    Preparation can prevent problems large and small.

    By Annie Crawley November 19, 2020

    Don't take basic equipment like masks for granted – it can make or break a dive.

    Even with nearly 10,000 dives, I’ve only had my mask or regulator kicked off twice—both times by students—but I’ve had to clear my mask on every single dive. (If you see fins coming too close to your face, get your arms into action and push those fins away!)

    Twice I’ve had to deliver an alternate air source to a buddy, both during a safety stop. I prevent out-of-air emergencies by checking my own air supply—and my buddies’—multiple times on every dive. I’m vigilant about preventing incidents from occurring, and value continuing education for all divers. Nothing can ruin that trip of a lifetime like not being properly trained or prepared for the adventure you seek.

    Recently, I taught a weeklong Rescue Diver program. The skills students learn in this class—and what dive professionals gain teaching it—will change your diving life forever. I recommend all my students become rescue divers, and also recommend they invest in dependable dive gear from their local retail dive center.

    Breaking down important considerations and protocols will help you “dive like a pro” and recognize and prevent in-water emergencies.

    1. Consider the ABCs of diving: airway, breathing and clearing, on every dive. Even the most experienced divers can have an issue if their eyes, ears, nose or mouth unexpectedly come into contact with water. At the surface, make sure you inflate your BC and are positively buoyant. Have your snorkel or regulator in at all times, to keep your airway clear. When changing between them, dip your face in the water to avoid swallowing water from a passing swell. I know many divers skip the snorkel in pool-like conditions, but wind and weather can change during a dive, turning that “pool” into a washing machine with 3-foot waves. I’m always kitted with a snorkel, on every dive, in case of changing conditions.

    2. Never force your ears to equalize. If you are prone to congestion, check with your doctor. Find a decongestant that works for you. You can get snotty on any dive; knowing how to blow your nose into your mask is an art form. Sometimes when you have difficulty equalizing, you have one stubborn piece of snot in your ear canal. You are stronger than your ears and can hurt them if you push too hard—always relieve pressure by ascending to a shallower depth or to the surface to blow your nose.

    3. A comfortable, properly fitted mask is the No. 1 piece of personal equipment a diver carries. If you or your buddy struggles with mask issues on a dive, it can ruin the dive. There’s nothing worse than a foggy mask—except a night dive with a foggy mask. After you rinse the defog from your mask and seat it on your face, don’t break the seal; if you do, you will need to re-defog your mask.

    During your dive, if you smile, adjust your reg or your mask strap moves on the back of your head, your mask may leak. Clear your mask. If it fills with water again, usually your mask strap is too high or low on the back of your head, or too tight or too loose. The mask could be riding up, giving you a rabbit nose, or falling down over your lips—either way, it breaks the seal and causes a leak. It’s physics.

    Exhale through your nose and move your mask around on your face to seat your mask properly. Adjust your mask strap and check again. A leaky mask can lead to congestion and equalization issues. If you get water in your mask, you can inhale the water, leading to issues with airway control.

    4. Create a routine for every time you dive. Set up your equipment the same way every dive.

    Together with your buddy, do a precheck on your equipment. Remember BWRAF: Begin With Review And Friend, Big White Rabbits Are Fluffy, Beer Wine Rum And Fun—no matter the acronym you choose to use, be sure to check all points and talk about your dive plan before getting into the water.

    ·                            BCD: Make sure it is on properly and you know how to operate it.

    ·                            Weights: Do you have the correct amount, and do you know how to release yours or your buddy’s if needed?

    ·                            Releases: Check all releases including tank release.

    ·                            Air: Do you have a full tank? How do you communicate air issues?

    ·                            Final check: Discuss your dive. I teach this “pre-check” before getting into our exposure suits; our “buddy check” before we get in the water goes quickly because any issues were spotted in our pre-check.

    5. Inspect your mask straps, fins, compass, dive knife, gear collecting bag. Have you bitten through the mouthpiece on your regulator? If you are wearing a hood, have you adjusted your strap to compensate so it is not too tight on your face? Carry a dive slate and dive light with you on every dive. If you are renting gear, does the needle on your air gauge read zero when the air is off, or is it permanently stuck at 500? How did you learn to show air?

    I recommend showing how much air you use with your buddy every 500 psi/40 bar. That way, both buddies are aware of how to adjust their dive plan throughout the dive so they will never run out of air, while maximizing their dive plan and time underwater. Review hand signals.

    Remember to ask for help not because you are weak, but because you want to become a stronger diver.

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