Daniel Farriott commands the JPC, first of a new class of nuclear submarine. While performing maneuvers off the Big Island of Hawaii, the submarine's drive train is disrupted in a freak accident, and the submarine sinks, settling upon Loihi Seamount, an active undersea volcano 3000 feet below the ocean's surface. While would-be rescuers and salvagers work feverishly above, the crew below takes what measures they can to survive in an increasingly hostile environment