Normal human divers every 10m dive, his body by the water pressure increased 100000Pa. For diving below 10m diver, in order to avoid decompression sickness danger, must develop a detailed decompression time program, that is, carefully calculated his up time and decompression time. For example, the diver to dive 40m deep, stay in the water for 50min (which includes the time used to dive to this depth), in order to ensure his safe return to the surface, the required surfacing time and decompression time total *** about 61min; which the diver must stay at a depth of 9m 5min, in 6m and 3m depth each rest about 20min. if the diver dives to a depth of 120m and stays 20min, the decompression time required will be as long as about 180min. In the deep sea, some fish are not affected by the pressure is because they have their own specialized decompression device