The experienced deep-sea divers Engel, Mitchel and Hurst have been assigned to repair an old oil pipe 200 meters below the Indian Ocean's surface, along with the newcomer Jones. Once their bodies have adapted to the extreme depth, it is impossible to quickly reach the surface without risk of decompression, which can lead to death. Suddenly a heavy storm comes in across the area, and the turmoil causes their diving clocks to break. The chance of rescue is slim, and the oxygen is starting to run out. Now they are forced to cooperate in the struggle for survival and to get back up to the surface.