A young thirty-something couple goes on holiday to the Caribbean. One of the fun activities available to them is scuba diving off a reef several miles out. Due to a faulty head count taken by the dive boat crew, the couple is left behind in the open ocean. They find themselves drifting endlessly for hours on end, facing dehydration, saltwater sickness, jellyfish stings, and sharks! Although a boat and a large ship pass by within the couple's view, neither sees them, and they are not discovered missing until the following morning when a member of the dive boat crew discovers their gear on the boat, and their hotel manager discovers they never returned to their room. Frantically a search is mounted by plane, boat, and helicopter, looking for the missing couple.