Being caught in the total darkness of an underwater cave is not fatal in and of itself. Nevertheless, it has been a contributing factor in several cave-diving fatalities.
- Loss of sight, due to light failure, contributes to disorientation and a sense of panic. Panicky, disoriented divers often make mistakes that divers who can see do not.
- Divers blinded by loss of light will have difficulty finding the guideline that leads to the cave entrance.
- Even when lightless divers are in physical contact with the guideline, it will take them longer to reach daylight than it would were they able to see. At this point, the question becomes whether they have sufficient breathing gas to make it to the exit.
Try the following experiment: Time how long it takes to walk from where you are now to the closest exit. Repeat the exercise with your eyes closed. It will almost certainly take longer.
- Because of the hazard that loss of light presents, we teach cave divers to carry at least three dive lights — one primary light and two backups.
- Cavern divers, who keep the cave entrance in sight at all times, carry at least one primary and one back-up light each. The sun counts as their third light source.
Although almost every cave diver eventually experiences a light failure, the odds that all members of a buddy team will experience a triple light failure are astronomically slim.