Risk and Redundancy

Modern dive computers can give us a wealth of information, but what if yours fails?Equipment redundancy, or having a backup, can help you know your true circumstances and prevent an injury or dangerous situation.

By Doug Stracener

My buddies and I were on a dive boat with several groups of divers who were planning to dive a reef. I was diving with enriched-air nitrox containing 32 percent oxygen (EAN32) to a planned maximum depth of 110 feet (33.5 meters) with two other divers. My primary computer was air integrated (connected to the high-pressure hose and in a console) and several years old.

The dive began as usual: I descended slowly while routinely monitoring my gauges to keep track of depth and remaining gas. As I neared the maximum operating depth (MOD) of my gas, I began to check my depth more frequently to make sure that I did not descend too far. On one of these routine checks I noticed that the depth displayed on my computer had not changed, but the water around me was considerably darker. I stopped the descent to check the computer more carefully, and to my surprise the display dimmed, flashed on and off several times and then died completely. It quickly became apparent that the computer had flooded and was shooting a small stream of bubbles from the case.

Fortunately, I always carry an analog submersible pressure gauge (SPG) and a backup wrist dive computer with me when I dive. This incident shows precisely why you should have redundancy in critical pieces of dive gear.

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Because of the extra equipment I had with me, I was able to quickly check my wrist computer and determine that I was slightly below my working depth of 110 feet but still inside the 130-foot (39.6-meter) MOD for EAN32 when my console computer failed. The analog SPG showed plenty of gas using the rule of thirds. After I notified my buddies, I ascended to 60 feet (18.3 meters) to join another group of divers from the same boat and had a normal 45-minute dive on a beautiful reef.

Afterward, divers aboard the boat had a serious discussion about what could have happened in this situation to a new diver with limited experience using a single air-integrated computer system. The consensus was that new divers may not even be aware of the hazard or the easy solution.

This experience is a great example of having the proper equipment for a planned dive and being prepared with appropriate emergency procedures in case of equipment failure. Dive computers can and will fail, and divers should plan for an inevitable failure. With air-integrated computers, it is especially important to also carry an analog SPG so you know your gas reserves at all times, particularly in the event of a computer failure. Because I also had a redundant dive computer, I was able to continue diving and avoid staying out of the water for 24 hours to revert to diving by tables. I kept myself safe while maximizing my time in the water.

Stay Prepared

Always consider “what if…” before a dive, and have a backup plan. All equipment can fail, and you’ll be better able to handle a situation if you’ve rehearsed an emergency plan than if you try to figure it out in the moment.

Opt for redundancy when possible.

  • Both traditional and air-integrated computers can fail, usually at depth and without warning. A backup SPG and computer can save a dive trip and keep you safe in an emergency situation.

Know your equipment.

  • Study your computer’s manual, and learn the information it contains.
  • Know how to interpret the computer display.
  • Download to your phone a PDF copy of your dive computer owner’s manual. Most manufacturers provide these files for free on their websites. When you cannot figure out how to operate the computer while sitting on a dive boat, having access to the manual can save a dive and help avoid accidents.


© Alert Diver — Q4 Fall 2018


Diagnosis Difficulty: DCI or Something Else

Diver experiences facial numbness and headache: DCI-related or another cause?

In this incident the symptoms that presented could have been attributed to several causes. This is a challenge DAN often faces when a diver calls for help.

A 63-year-old male was on a diving holiday in Papua New Guinea. A call was made to the DAN Diving Emergency Service (DES) Hotline as the diver was experiencing symptoms following two dives he completed the previous day:

  • Dive 1: Depth of 22 meters for a total dive time of 40 minutes, with a surface interval of 2 hours and 30 minutes.
  • Dive 2: Depth of 32 meters for a total dive time of 116 minutes. Long decompression with most of the dive spent at 24 meters.

Both dives were on Nitrox, with no issues noted on either dive.

Twenty minutes after the dive he developed a headache and then numbness around the left eye and around his mouth. The DAN diving doctor performed a neurological assessment over the phone, which the diver completed satisfactorily.

The DAN doctor suggested that the diver go to the local clinic for oxygen first aid. The clinic did not think his condition was DCI-related, so did not give him oxygen treatment. Doctors at a larger hospital advised he was likely to be experiencing DCI.

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The next day the diver’s symptoms progressed to numbness all over the right side of his face and a feeling of facial drooping. DAN staff was concerned that the diver had possibly experienced a stroke but were still not ruling out DCI. While there is a hyperbaric chamber in Port Moresby, DAN recommended the diver be evacuated to Townsville, QLD, for a higher level of care due to the ambiguity of his symptoms.

DAN asked that the diver remain breathing oxygen for as long as possible as the evacuation was organised. Once in Townsville the diver received a single chamber treatment, but there was no change in his symptoms.

After undergoing testing, the diver was diagnosed was Bell’s palsy, which the doctors believed could be coincidentally associated with diving. The diagnosis was reviewed by a neurologist, after which the diver was discharged to return home. Bell’s palsy is paralysis or weakness of the muscles on one side of the face. The exact cause is unknown and most people with Bell’s palsy recover completely with time.

DAN Comment

This incident highlights one of the challenges DAN faces when a call for help is received. The DAN Diving Doctor discusses with the diver:

  • Their dive profiles
  • The symptoms they are experiencing:
    • What they are
    • When they developed
    • Their progression – Have they become worse? Have new symptoms appeared?

Sometimes, from the information provided, it is not clear whether the diver is experiencing DCI and needs to receive recompression or whether the cause is attributed to another cause, such as stroke or a cardiovascular-related incident. The priority in these cases is to get the diver to higher-level care for further assessment and treatment.

Symptoms of DCI Return After Flying

Symptoms Return After Flying: Did the Diver Fly Too Soon?

flying after diving


In this incident, a diver was evacuated for recompression, but flew home sooner than DAN advised, and unfortunately the symptoms returned and persisted for some time. Could this have been avoided if the diver had delayed his flight home?

The Dives

A 28-year-old dive instructor completed a long 45m dive on mixed gas with decompression. The next day he completed a dive (on air) to 26m for 65 minutes and afterwards noted that he felt more tired than usual.

Symptoms Present

The following day, more than 24 hours after his final dive, he felt an ache/burn in his right shoulder. By the time he called DAN on the next day, he had some altered sensation in his hip and elbow. He had been receiving oxygen first aid for six hours without any significant improvement when he decided to call DAN.

DAN’s Advice

The DAN Diving Emergency Service (DES) doctor was not certain the diver was experiencing DCI based on the information provided. The doctor asked the diver to continue breathing oxygen for a few more hours that evening, take ibuprofen and reassess his condition the following morning.

As the diver was in Timor, where there are no chamber facilities, he would need to be evacuated for treatment if symptoms did not improve.

When DAN spoke to the diver the following day, he advised that he had remained on oxygen for an additional six hours the evening before plus another hour that morning. He thought the ibuprofen relieved the feeling of pressure in his lower back but advised the pain in his right shoulder and the hypersensitivity in his shoulder, arm and chest area were still present, along with the discomfort in his right hip. He was also getting waves of pain in his right elbow and had a stiff right little finger. When he attempted some light activities with his clients he felt short of breath and his breathing was difficult.

Evacuation Required

The DAN doctor advised the diver to see a hyperbaric medicine specialist and that recompression was a possibility. An evacuation to Darwin was impossible — the diver did not have a visa to enter Australia and an emergency visa was not readily available — so the evacuation was directed to Singapore at a cost of USD$34,500.

While waiting for the evacuation the diver breathed oxygen for another three hours and felt much better. In fact, he nearly called DAN to say he was better, but that evening the symptoms returned.


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Once in Singapore, the diver’s evaluation resulted in two recompression treatments. His symptoms mostly resolved but he did express to the doctor that he still had shoulder discomfort after treatment. The doctor believed it was not DCS and discharged him from hospital.

Conflicting ‘Do Not Fly’ Advice

The dive medicine doctor advised the diver not to fly for three days, but DAN advised that this was insufficient and that he should wait at least a week before flying back to Timor given the remoteness of his destination.

The diver ended up flying home four days after treatment and upon his return the diver informed DAN that he was experiencing residual symptoms in his hip, shoulder and elbow.

The DAN doctors advised the diver to continue taking ibuprofen for several days to help with the residual inflammation, remain hydrated and refrain from exercising or going to altitude. The diver’s condition did not deteriorate further, but to his frustration, improvement was very slow.

DAN Comment

While the diver’s symptoms in this case were mild, they were persistent. The diver was evacuated to Singapore and received two treatments, and unfortunately, he did not follow DAN’s advice to avoid flying for at least a week.

In many cases divers are cleared to fly after three days from their final treatment if they remain asymptomatic. This is often fine and many divers following this advice have no further issues — although a small number will.

In this case, the advice by DAN factored in the remoteness of the diver’s location to suggest waiting longer than the doctor’s recommendation. Once the diver flew home to Timor, his symptoms reappearing would put him back in the same situation: experiencing DCI in a location that was not equipped with higher level medical care, including a chamber.

Flying aggravated the diver’s condition, as he likely had residual bubbles in his system, and as such it took a longer time for his persistent symptoms to fully resolve.

This case serves as an important reminder to adhere to the advice of DAN, as our case managers factor in all aspects of a diver’s situation when providing advice.

You can review DAN’s Flying After Diving Guidelines HERE.


Plan Your Dive, Dive Your Plan

dive planning-2.jpgDive Planning

One of the most important things you can do before diving is dive planning. Learn as much as possible in advance about any site you plan to dive.

  • Before you even head out to a site, make sure to investigate currents, depths, marine life, entry and exit points, surfacing techniques, boat traffic, environmental health concerns, etc.
  • Check out what surface support you may need and what local laws or regulations may apply to your planned diving activity.
  • Inform someone who is not coming on your trip what you plan to do and when you expect to be back.
  • Prior to your dive, make sure you and your buddy have the same dive plan. Discuss contingencies should conditions change during your dive. Establish the maximum depth, maximum bottom time and minimum air supply to terminate the dive.
  • Review what you and your buddy would do if you were to become separated, exceed your planned dive or experience an out-of-air emergency or equipment problem underwater. Having these discussions on the surface helps you prepare as a buddy team to manage any situations that may arise while underwater.
  • Review hand signals with your buddy.
  • Conduct a predive test on all your equipment, particularly any rented gear. Use a written or mnemonic checklist to ensure you don’t overlook an essential step. Don’t skip the buddy check.
  • Remember to create an emergency action plan (EAP). This essential tool, which divers are taught how to construct in their advanced training courses, should include what prompts an emergency response, important contact information, the nearest medical facility and the best means of getting there as well as essential first aid equipment.

Dive plans don’t have to be complicated or inflexible, but they are essential for preventing and managing diving incidents.


Buoyancy Control

It’s not surprising that the most common injuries among divers are related to buoyancy issues — barotrauma, uncontrolled ascents, marine life injuries and more can be prevented with some practice and attention to detail.

  • Inefficient buoyancy control can result in descending deeper than planned, altering the intended dive profile and potentially increasing air consumption. Constant adjustments to your buoyancy control device can also affect air consumption.
  • The worst-case scenario is an uncontrolled ascent, which places the diver at risk of a lung overexpansion injury (pulmonary barotrauma) and substantially increases the risk of an arterial gas embolism.
  • Ear injuries are also commonly associated with ineffective buoyancy control. During descent, if you feel uncomfortable pressure in your middle ears or sinuses, you should stop your descent, ascend until the pressure resolves, attempt to equalise and, if successful, continue to descend. If you experience a reverse block on ascent, you should descend a bit and attempt to equalise. These procedures are difficult to execute without proper buoyancy control.
  • Most marine life injuries result from unintentional contact between a diver and the marine life. Proper buoyancy control is essential to protect ourselves and the environment.

The physics of descending and ascending require conscious adjustment based on exposure protection, dive environment and choice of equipment.

Buoyancy Control Begins with Proper Weighting

  • The amount of weight you select should allow you to descend, not make you sink. Predive buoyancy tests are crucial for determining proper weighting.
  • When calculating weight requirements, different exposure suits, dive environments (saltwater vs. freshwater) and cylinder size and composition (steel vs. aluminium) require different amounts of weight to attain proper buoyancy.
  • Your BCD is not an elevator. Be aware of how your BCD responds to addition or venting of small amounts of air.
  • And remember, your buoyancy will change during the dive. On descent your wetsuit compresses, decreasing buoyancy. During the dive, as the gas in your tank is depleted, the tank becomes more buoyant. On ascent, the air in your wetsuit and BCD expands, increasing your buoyancy.

Good buoyancy control enhances your diving and helps you avoid injury. The benefits are definitely worth the investment of time, maintenance and practice.

Never Dive Beyond Your Training

As a diver, you should never stop developing your diving abilities. There is always more to learn —how to dive new environments, how to refine your skills and even how to use new types of equipment. No matter where your diving adventures take you, make sure you are equipped with the proper training.


  • Your certification only qualifies you for the same diving conditions and environment in which you were trained.
  • As you continue your training, slowly extend your diving experiences. California shore diving presents different challenges than Caribbean boat diving — make sure you’re prepared for each new diving environment.
  • Take it easy, and if you’re not having fun or if you don’t feel good about the dive, don’t do it. This is especially important when diving in new conditions such as cold water or limited visibility or when using new equipment.
  • If you feel uncomfortable about a dive, it may because you feel that you’re not ready. Remember, dive your experience, not your “C card.”
  • If you want to begin exploring new environments, seek the training that will prepare you to explore them safely. For instance, if you want to explore the interiors of shipwrecks or enter a cave, enrol in a wreck diving or cave diving course. These unique overhead environments present specific challenges that can be deadly if you are not trained to manage them.

Your Gas Supply

Running out of air is the most common trigger for diving accidents. It seems like a no-brainer, but several factors can affect consumption rate. Be air aware: Monitor your gas supply.

  • Incorporate gas supply into your dive planning. You can only stay under for as long as you have enough gas remaining to do a safe ascent. Don’t forget to save some gas for flotation.
  • Check your gauge regularly.
  • Be aware that exertion, such as when swimming against strong currents, and depth will affect your air consumption.
  • Anxiety or stress can also affect air consumption. Try to maintain normal breathing, but if you do feel anxious, keep a closer eye on your gas supply; it may dwindle more rapidly than usual.

Take Personal Responsibility

Each diver in the dive group shares responsibility for the conduct of the dive. When all divers understand and agree with that premise, the dive group can protect itself from individual and collective harm. Know your personal limits, and take time to examine and evaluate your dive habits. Don’t rely on the experience of other divers in the group. As a certified diver, you are expected to recognise when elements are outside your level of training or comfort zone; it is your responsibility to acknowledge that and voice it. Always remember, anyone can call off a dive at any time. In other words, it’s always OK to say “No.”

We hope these reminders help you get your year off to a safe start and will be carried with you through the year and beyond. Have a great year of diving, and if you need help, DAN is just a phone call away, 24/7: +61-8-8212 9242

Start the New Year Off Right!

Your Health and Fitness


When health issues are present, it’s important to discuss them with your healthcare provider, pursue appropriate interventions and, if necessary, modify your diving.

Prior to diving, you should take an honest assessment of whether you are medically fit to dive. Be vigilant for signs of acute illness (such as congestion) and familiarise yourself with the risks and essential precautions associated with chronic diseases.

Acute illnesses that last more than a few days or leaves you feeling exhausted should prompt a delay to diving.

  • Do not dive when ill.
  • Wait until you regain your normal strength and stamina.
  • If you are not ready to exercise at your pre-illness level, postpone your dive.
  • The best course of action is to consult your physician.

Chronic diseases may affect your fitness to dive even if you perform well in other activities.

  • Some health conditions, especially in advanced stages, may make the risks to you and your dive buddies unacceptably high.
  • With less advanced or more stable medical conditions, divers may continue safe and enjoyable diving with medication, guidance from their physician and wise choices.

During your annual physical exam or following any changes in your health status, consult your physician to ensure you have medical clearance to dive.


Being a physically fit diver means that you have sufficient aerobic capacity, cardiovascular health and physical strength to meet the demands of the diving environment. Can you fight a current? Perform a long surface swim? Help a buddy in an emergency? All divers need to be physically able to perform these essential tasks.

While diving itself can be physically demanding, maintaining overall fitness requires additional physical activity beyond just diving. Here are some tips to help you enhance your fitness for diving:

  • Regular physical activity, including aerobic activity and muscle-strengthening activity, is essential for maintaining physical fitness; try swimming laps, strength training or flexibility and balance exercises.
  • If you are over 40 and do not exercise regularly, consult your physician before you start exercising.
  • Dedicate time to fin swimming. Swimming with fins will strengthen muscles that other aerobic activities won’t. Even if you have high aerobic capacity for muscular work, you may find yourself unable to overcome a strong current if you never practice swimming with fins.
  • At least six weeks prior to a dive trip, gradually increase the level of your physical activities.
  • Join your local dive club for more specific training opportunities.

To avoid an increased risk of decompression sickness, DAN recommends avoiding strenuous exercise for 24 hours after diving.


Proper Gear Maintenance

shutterstock_146570078_webDive equipment is life-support equipment. Each time you dive, you are venturing into a fascinating but also unforgiving environment; make sure you are diving with properly functioning equipment.

One of the best ways to keep your gear functioning properly is to keep it well-maintained. Here are some easy ways to do that:

  • Rinse your equipment after each dive, and clean it after each trip before storage.
  • After rinsing, allow gear to dry completely in a cool, shady and well-ventilated area before you put it away.
  • Store your gear in an area that is protected from extreme temperatures as well as dust and dirt.
  • Whether you use your equipment frequently or only for annual dive trips, get your gear professionally serviced to ensure all parts and pieces are working properly.
  • Regularly monitor your equipment for signs of wear and check the hoses for leaks or cracks; pay particular attention to your regulator.
  • As part of your annual equipment overhaul, have your pressure gauge checked for accuracy.
  • Most divers are diligent about their regulators, but BCDs are often overlooked. The bladder and low-pressure inflator hose are both subject to deterioration and should be inspected at the same time the regulator is serviced.
  • Replacing parts as needed prolongs the life of your equipment and helps prevent incidents such as uncontrolled ascents and regulator failure underwater.
  • Follow manufacturer’s guidelines on proper maintenance of your equipment. If you have questions, contact your local dive centre or the manufacturer.
  • Take an equipment maintenance course to learn even more about gear maintenance.

For more information about health and diving, visit DAN.org/Health and check back in for next week’s post about buoyancy control, dive planning and more.

DCI, Dehydration or a Cardiac Event in PNG?

While on a diving holiday in Papua New Guinea (PNG), a diver experienced symptoms that could have been attributed to DCI, dehydration or a cardiovascular-related event.

DCI, dehydration or a cardiovascular-related event? In this recent case in PNG, DAN made the decision to evacuate the diver, and had to factor in the treatment he could possibly require once he underwent medical tests.

Continue reading “DCI, Dehydration or a Cardiac Event in PNG?”

Tingling and Nausea in Malaysia

Among the variety of challenges that DAN faces when attempting to arrange an emergency evacuation for a diver: pirates!

Among the variety of challenges that DAN faces when attempting to arrange an emergency evacuation for a diver: pirates! Continue reading “Tingling and Nausea in Malaysia”

Suspected DCI in the Philippines – numbness in hands

A diver in the Philippines suffers numbness in hands, but could have avoided recompression treatment, if DAN had been called first and the advice of our diving doctors followed.

Similar to the Manado case last week, in this case study, a diver in the Philippines suffers numbness in hands and received one recompression treatment, but this could have avoided recompression treatment, if DAN had been called first and the advice of our diving doctors followed.

Continue reading “Suspected DCI in the Philippines – numbness in hands”

Dizziness and Tingling in Manado

A new diver accidentally misses her safety stop and experiences DCI-related symptoms.

A new diver accidentally misses her safety stop and experiences DCI-related symptoms.

This Member completed a dive to 18m for a total dive time of 40 minutes the previous day. She had forgotten to complete her safety stop when ascending, so decided to descend again to 5m to complete it. Continue reading “Dizziness and Tingling in Manado”

The jet boat driver used my dive flag as a target! Readers share their near-misses.

Last week we put a call out asking divers to share incidents concerning boat safety, and we received some interesting stories. Fortunately, in these cases there were no injuries, but the outcome could have been very different. Following is a review of the encounters: Continue reading “The jet boat driver used my dive flag as a target! Readers share their near-misses.”

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