Taking scuba now and they basically said you have to be in somewhat decent shape because the more your have to exert yourself the more likely you are to die.
I found this passage about a world class deep divers fatal dive where he basically became exhausted and died educational.
"Shaw died on 8 January 2005 while seeking to recover the body of Dreyer.[4][5]
Shaw recorded his dive with an underwater camera, which allowed researchers to determine that he suffered from respiratory issues due to the high pressure.[6][7] Shaw ran into difficulties when he cut loose Dreyer's harness and the body unexpectedly began to float. Shaw had been advised by various experts that the body would remain negatively buoyant because the visible parts were reduced to the skeleton. However, within his wetsuit, Dreyer's corpse had turned into a soap-like substance called adipocere, which floats. Shaw had been working with both hands, and so had been resting his can light on the cave floor. The powerful underwater lights that cave divers use are connected by wires to heavy battery canisters, normally worn on the cave diver's waist, or sometimes attached to their tanks. Normally he would have wrapped the wire behind his neck, but he was unable to do so; the lines from the body bag appear to have become entangled with the light head, and the physical effort of trying to free himself led to his death. The next day, both of the bodies floated up to near the surface as the dive team was retrieving their equipment.
The dive on which Shaw died was the 333rd dive of his career. At the time of his world record setting dive, he had been diving for just over five years."
