The player is trapped in a crashed nuclear submarine which has begun taking on water. They need to escape by making their way up the levels of the submarine one at a time. Each floor has two hatch keys that need to be collected in order to unlock the elevator to the next level. There is a time limit, though; if you take too long the floor will flood and you'll be unable to escape. Due to the crash, the torpedoes on board the submarine are now loose and wander across the floor as the boat shakes. The player will need to jump over any torpedoes that cross their path, or they will be stunned momentarily and lose precious time.
31st December 1982