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.


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 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.

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 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 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