Sea Hunt

A jet plane suddenly goes out of control, plunging to the bottom of the sea. When ex-Navy frogman, Mike Nelson dives to locate the wreck, he's amazed to find the pilot still alive, imprisoned in the watertight cockpit. Mike estimates there's less than fifteen minutes of life-giving oxygen left. And he knows that if he opens the canopy, the ocean's pressure will crush the pilot.

An explosion rocks a Wyoming coal mine, flooding the shafts and costing the lives of 30 miners. Mike Nelson dives to locate the cause of the disaster. Deep in the shafts, Mike discovers two survivors trapped in an air pocket. It looks like Mike can only get one of them out, leaving the other to perish.

When deep sea divers go too deep or stay down too long, they suffer from an excess of nitrogen in the bloodstream. The resulting narcotic effect is called "Rapture of the Deep." When a party of skin divers falls victim to the "rapture," one of them becomes homicidal.

Before Mike Nelson can investigate the disappearance of two geologists the sea washes one of them upon the beach, his body bearing marks apparently made by the suction valves of a giant octopus. When later the body of a young boy is found with the same mysterious marks, Mike is sure that the killer is a diabolically clever man who has somehow found a way to duplicate the mark of an octopus.

Mike Nelson rescues an unidentified girl from drowning. The Immigration Department suspects she's an illegal alien. Released in Mike's custody, the girl confesses she was towed into the country underwater in a sea sled operated by a ring of border-runners.

Lovely Kay Dalton, terrified of the sea, persists in skin-diving. Her objective is to recover a cache of stolen diamonds on the ocean floor. Although Mike Nelson warns that she will never conquer her fears, Kay refuses to quit.