Instead they will start a slow ascent, to let the accumulated nitrogen in their tissues bubble out slowly. To go deeper would shorten the safe dive time considerably and risk the bends, a brutal pain that comes from nitrogen escaping too quickly and forming large gas bubbles that interfere with circulation. Another potential problem of going deeper is simply running out of air and drowning. The beauty of scuba, which stands for self-contained underwater breathing apparatus, is that you are free of any connection to the surface, and can go where you will. So divers pace themselves, and rarely run out of air.
Strict guidelines mandate how deep to go, how long to stay and how quickly to ascend.
As a result, thousands of dives have been made here, on this wall, with no fatality and only a few mishaps. Problems have occurred mainly when divers foolishly went too deep or stayed too long. Periodically the divemaster turns around to count heads. Her job is to guide the dive and try to make it memorable, even exciting. At a depth of 82 feet she spots a giant crab hiding in a coral crevice.