Diving in an Overhead Cavern With Half Empty Tanks

Two imprudent divers learn cavern diving rules the hard way.

Reported Story

A 25-year-old female diver performed a second dive on a 63 cubic foot tank (~9 Litres*) without refilling it. The diver ran out of air at about 50 fsw (15 msw) in an overhead environment. While exiting the cavern breathing from the other diver’s alternate second stage, the divers became entangled in a line. While attempting to free themselves, the second diver also ran out of air. The divers conducted an emergency swimming ascent out of the cavern and then made a rapid ascent the last 20 feet (6 m) to the surface. Both divers inhaled water during the ascent. Upon reaching the surface the divers were given emergency oxygen and EMS responded to the scene. The husband refused treatment, the wife was transported to the hospital where she remained overnight for observation and was then discharged.


Twice as many untrained cavern or cave divers have died in U.S. caves than properly trained cave divers. When the water is crystal clear and the sun shining outside, inexperienced divers might be tempted to enter these overhead environments for a thrill. Sadly, hundreds of these untrained divers have died in the US. To safely dive into caverns or caves requires cavern or cave diver training. These two divers were lucky to survive and they are surely the exception. It is hard to imagine many other divers running out of gas in a cave and making it out alive. Cavern diving can be an exciting type of specialized diving but make no mistake, there are no shortcuts to this activity, only shortcuts to the grave. Training is required before going in, no matter how bright the sun is outside or how clear the water in the cave.

Peter Buzzacott, MPH, Ph.D.

Note: In the U.S., it is common for a nine-liter tank to hold 63 cubic feet of compressed gas, so that is the equivalent volume suggested here in brackets.