Zale Parry

Before Mike Nelson can investigate the disappearance of two geologists, the sea washes one of them upon the beach. His body bears marks made by the suction valves of a giant octopus. Mike knows an octopus rarely attacks.

Lewis Hale tells Mike that he has invented a machine that locates sunken ships laden with gold. Mike discovers the machine is actually a stolen Top Secret U.S. Navy device and pitches into a life-or-death struggle with Hale to retrieve it.

A coastal fisherman wages a private war against kelp harvesters in his area. The fisherman has a diabolical scheme to destroy the kelp harvesters' boat with a mine, but Mike steps in to prevent a tragedy.

Skin-diving fans Robert and Maria Tyler explore the sea with an underwater camera. But only Mr. Tyler returns. Mike Nelson uses an underwater photograph to test the truth of Tyler's story.

Six sportsmen rent an amphibian plane to fly them to a skin-diving site. When one of the divers, using a Sea Scooter, mysteriously disappears, Mike searches and finds him–photographing secret Navy installations!