An Italian submarine returns from a mission. The crew members look forward to reunite with their family, and to escape the promiscuity that causes tensions to run high amongst sailors. Shortly before reaching safe waters, disaster strikes: a squadron of enemy airplanes bombs the submarine, which sinks to the bottom of the sea, 110 meters below the waterline. The captain immediately decides to evacuate the survivors via the onboard rescue capsule, but before he can start the tedious process of sending his men one by one to the surface, difficulties accumulate. The grievously wounded sailors found in one of the submarine compartments must somehow be dealt with. And he quickly realizes that this is the least of his problems...