Accident analysis and safe cave diving

Photo: Steve Straatsma

Accident analysis over the years has played a big role in developing the safety guidelines for safe cave diving. The NSS-CDS in the late 1970s organized a study of the cave diving fatalities for which information existed. As a result of this study, Sheck Exley discovered that three primary safety violations accounted for, at least part of, all of the fatalities. The three safety violations were the beginnings of organizing a list of safety guidelines that could be taught to new cave divers and shared with current cave divers in the hopes of making cave diving as a whole much safer. In 1984, Wes Skiles, who was the Training Chairman for the NSS-CDS, expanded the safety violation list to account for two other accident-contributing factors.

The five safety violations that were discovered during the studies are:

· Failure to be properly trained or exceeding the level and limits of one’s training
· Failure to use a continuous guideline from the entrance of the cave and throughout the dive
· Failure to reserve at least two-thirds of the beginning gas supply for exiting the cave
· Failure to limit the dive to the operational limits of compressed air (130 fsw)
· Failure to carry at least three battery powered lights

These five safety violations that stood out in every one of the fatalities studied were presented to every cave instructor, cave diver, and to any diver who would listen. As more and more divers learned about these safety violations, fatalities began decreasing in the cave diving community. The five safety violations became the mantra for safe cave diving almost to the point that nothing else was looked at or investigated. The premise that if you followed these five rules, every cave dive you did was a safe cave dive was spreading in the cave community. Accident analysis was stalling as if there was nothing else to learn.

Fortunately, that wasn’t the case and accident analysis still exists today. It is an important platform for evaluating accident-contributing factors and using what is learned to expand teaching and education in the cave diving community. Accident analysis isn’t foolproof or the only way to expand and learn how to safely cave dive. While each of these rules played a part in every one of the cave diving fatalities that were studied, they don’t reveal the sequence of events that lead to the accident. There are other factors that can play significant roles and that have played significant roles in cave diving accidents or near misses. It is important to look beyond the five safety rules and not interpret them so strictly that you can’t see anything else. Accident analysis is about learning and discovering so that this information can be shared and used by everyone. If you refuse to look beyond these five basic violations or misuse them to justify attempting dives outside your level of training or experience, you’re putting yourself and your buddy in jeopardy. Don’t let yourself become an accident analysis study victim because you refuse to look beyond these five basic rules.

A closer look at the five rules

Proper training and not exceeding your skill level and limits is the primary reason for cave diving accidents. Many of the cave diving fatalities over the years have been because the diver wasn’t cave certified or was trying to do a dive that was well beyond his/her abilities. Without the proper training, cave diving can be an extremely dangerous sport. Cave diving requires a special mindset, special techniques and equipment, and procedures that you can only get in specialized cave and cavern diving courses. No amount of experience, number of dives, or open water certification level is enough to safely cave dive; you must participate in cavern and cave diving courses to conduct safe cave dives.

Using a continuous guideline from the entrance of the cave and throughout the dive is essential. Without a continuous line, you’re relying on memory to find your way out of a cave. Caves do not look the same on the way out as they did on the way in. Visibility can change, silt outs can occur, lights can fail, which all can contribute to getting hopelessly lost. A guideline to the cave’s exit is basically a lifeline; it’s the route out. Always run a continuous line from the entrance of the cave and throughout your dive. Don’t make jumps without running a gap line. Don’t assume that since you’ve dove the cave before that you don’t need to run a line from the entrance, things can change from dive to dive.

Always reserve at least two-thirds of your beginning gas supply for exiting the cave. This is also known as the Thirds Rule. Exhausting more than one-third of your gas supply for the swim into a cave does not allow for adequate reserve amounts. If you use one-third to go in, you’ll need one-third to exit and will have one-third for emergencies. The thirds rule is also extremely important in buddy teams. If a team member had a catastrophic gas loss at maximum penetration and had to rely on their buddy’s gas supply to exit the cave, the two-thirds of remaining gas would be required to get both divers out of the cave safely. Cave environments are not all the same, meaning that the thirds rule may have to be altered. If you’re diving in a siphon system, swimming out of the cave against the flow may require more than one-third of your gas supply, meaning that you may not want to go until you’ve used up one-third of your gas. Other adverse conditions may require a more conservative gas planning strategy as well. Each cave dive requires specific gas planning. Don’t just assume that the Thirds Rule applies everywhere.

Limit your dives to the operational limits of compressed air (130 fsw). Diving below 130 fsw on standard air increases the risks of nitrogen narcosis and the deeper you go increases your chances of getting oxygen toxicity. With the modern day advances and applications of mixed gas diving, there is no reason to dive deep on air. Trimix training is available through many of the training agencies. Mixed gas diving reduces nitrogen narcosis and oxygen toxicity, which in turns drastically increases the safety of a dive. If you can’t afford to get trimix certified or purchase the helium needed to conduct a dive, then limit your dives to recreational limitations of 130 fsw.

Always carry at least three battery powered lights on every cave dive. On a cavern dive, where the natural light acts as a third light, you only need to carry two battery powered lights. Lights are sometimes the most vulnerable pieces of dive equipment, meaning that they can fail easily. Bulbs can blow, wiring can fail, and batteries can fail. By carrying at least three backup lights, the likely hood of all three lights failing on the same dive are slim. In addition to just carrying the lights, you need to make sure you take care of your lights. Change your batteries frequently and make sure rechargeable lights are charged prior to the dive. If you have a lot of hours on a bulb, you may want to replace it before it fails. Without proper and reliable lighting, cave diving can be a vary dark sport.