“Here is what happens to a panicked diver in trouble inside a shipwreck:

His heart and respiratory rates jump. At 200 feet, when every lungful of air requires seven times the volume as that on the surface, a panicked diver can breathe down his tanks so quickly that the needles on his gauges begin to drop into the red before his eyes. That sight further quickens his heart and breath, which in turn further reduces the time he has to solve his problems. Heavier respiration also means heavier narcosis. Narcosis amplifies panic. A vicious cycle has begun.”