An ominous reminder found on many cave signs cautions divers not to exceed their limits
Until the 1980s, cave diving had a sad history of frequent deaths. Analysis of accidents showed the following causes (percentages have been rounded).
No training in cave diving at all.
Trained cave divers diving deeper than 40 meters (note that at that time, helium was not in common use by cave divers so that nitrogen narcosis was a significant factor)
Trained cave divers who knew the rules for cave diving, but intentionally broke them
Mainly natural causes such as medical illness, and in just one case, the collapse of a cave
A healthy, trained, cave diver who dives shallower than 40 meters and who follows the established cave diving rules is very unlikely to have an accident
All Cave-Exploration divers have appropriate training and are physically fit and healthy. Our policy is to follow all of the established rules of cave diving, all the time, with no exceptions, and not to dive deeper than 40 meters in caves. As a result we believe that we are safer inside the caves than driving on the CF 307!