ACCIDENT REPORT

Two divers from Miami, Barry and Luke, drove up Thursday night, met some other divers and entered the water at Eagle's Nest Sink at 12:40 AM. Barry was an experienced cave and deep diver, but Luke, while experienced at open water diving, had only minimal experience at cave and deep diving. Despite the fact that Luke had never been below 200 ft. and both divers were tired from the long drive, a dive was planned to 270 ft. depth. When Barry and Luke failed to surface, the other divers called the sheriff's dept. on 6/2/72.

We found Luke's body at a depth of 260 ft., 500 ft. from the cave entrance, and Barry's inert form about 100 ft. closer at a depth of 240 ft. Both divers were completely out of air and the silt on the floor around the bodies did not show any signs of struggling.

ANALYSIS

Again several errors were made. A continuous guideline was used and the divers may or may not have planned their air properly (we have no way of knowing), but a diver with Luke's limited experience at cave diving did not belong 500 ft. back in a cave, especially at a depth at least 60 ft. deeper than he had ever been before. From the lack of signs of a struggle it would appear that both divers lost consciousness before running out of air, probably due at least in part to the effects of breathing compressed air at great depth.

HOW DEEP IS DEEP?

The sport diving community advocates limiting dives to 130 ft. or shallower and it would appear that there is a very good reason for it. An analysis by the author of cave diving accidents in Florida has shown that the small percentage of accidents where a continuous guideline and the "third rule" were used all involved dives to depths of 155 ft. or greater. Further, the shallowest depth at which "depth blackout" - the most likely cause of Barry and Luke's deaths - has been observed to occur is 150 ft.

THE DEPTH BLACKOUT

A victim of "depth blackout" appears to be asleep with his eyes open, and does not move other than continuing to breathe. It is not known why the victim retains his mouthpiece, but it's a fact that victims of depth blackout will go on breathing, lying inert on the bottom, until they run out of air.

An analysis of the diving history of the 15 known survivors of depth blackout has shown that in every case the problem occurred on the deepest dive they had made up to that time. The shallower instances also involved heavy exertion on the part of the victims. Perhaps most frightening is the fact that several of the victims do not recall feeling any unusual symptoms prior to blacking out. A vertical ascent of approximately 50 ft. was generally sufficient to bring the victims back to complete consciousness so that they could continue their ascent unaided. Depth blackout is probably the cumulative effect of nitrogen, oxygen and carbon dioxide - the chief constituents of dry compressed air — at extreme depth.

PREVENTION

The most important prevention of "depth blackout" is, again, to avoid deep diving. Chances are you'll hear of experienced cave divers occasionally going deeper than 130 ft. However, they do so only when utilizing very special equipment and procedures. One of these procedures is to build up an adaptation to depth very slowly over a series of repeated dives under controlled conditions in open water before attempting a deep dive in a cave. It is beyond the scope of this manual to go into detail regarding these procedures and we strongly recommend that you contact a highly experienced deep cave diver for personal guidance beforehand if you decide to ignore our warnings and attempt to deep dive in a cave anyway. It should be added that most of the small percentage of accidents involving experienced cave divers have occurred on deep cave dives.

SUMMARY

The small percentage of cave diving accidents where the victims did use a continuous guideline and the "third rule" all involved diving to depths of 155 ft. or deeper. The maximum safe depth for cave diving is .130 ft. Divers may actually "black out" from breathing air at greater depths, appearing to fall asleep with their eyes open until they run out of air and drown. The foolhardy who insist on diving to deeper depths anyway should contact experienced cave divers first for guidance.