Sheck Exley wrote a publication on cave diving safety in 1977 called, “Basic Cave Diving: A Blueprint for Survival.” He described true stories of cave diving accidents and detailed what could have prevented each one. Although a variety of mistakes can be made cave diving, Exley proposed that all cave diving accidents could be attributed to at least one of a handful of cardinal rules being broken.

The primary five rules Exley described are often recalled with the mnemonic “The Good Divers Are Living.” However, in the United States, many trainers teach the mnemonic “Thank Goodness All Divers Live,” with a switching around of the order of the five rules.

1) Training is vital for the cave diver. A safe diver will never push beyond the limits of what is taught to be safe and reasonable. Training goes in stages with each level more difficult than the last, adding greater knowledge and experience to earlier trainings.

2) Guide lines are used to connect the leader of the dive team to the outside of the cave entrance. It is a thin but strong rope that the team can follow back the way they came to avoid getting lost or turned around in the cave. Failure to use this is considered the most frequent cause of cave-diver fatalities as divers can so easily lose their way inside the caves and run out of air before they find their way out.

3) Depth rules are vital for divers to understand, because with increasing depth, more air and decompression are required. The maximum operating depth (MOD) is a depth that no diver should pass beneath without the potential for sudden death. And nitrogen narcosis is a real threat in a cave.

4) Air management is based on the “rule of thirds.” One third of the initial gas supply is allowable for ingress, a second third for egress, and the final third is reserved for saving a fellow diver should an emergency occur. But if there is little to no outflow from the cave, it is best to be even a little more reserved with the air supply.

5) Lights are so important in a dark environment that if a light source went out, the diver could become completely disoriented and lost. For that reason, all divers are recommended to use a primary source of light, bringing two additional sources as backup.

Following these five safety guidelines, especially after extensive training, can prevent potentially deadly incidents, making cave diving a much safer experience.