A sea monster kills three villagers in a Norwegian fjord; however, one man survives. Seaview arrives to investigate. Nelson and Crane are met with hostility from the locals and find the survivor has died. Nelson does his best to make sure the "sea monster" doesn't destroy Seaview.

Damaged by an explosion from an old mine field, Seaview takes a dive to the ocean floor. Listing dangerously, running out of oxygen, having to deal with fire and flood, the crew can do nothing but wait for help. But will help arrive in time?