While traveling in enemy waters, Captain Fathom and his crew detect an anomalous reading of radioactivity. The submariners investigate and discover a huge bomb lying on the ocean bottom. While Fathom fastens an explosive to destroy the atomic device, his ship is attacked by an enemy submarine. He orders the vessel to flee leaving the Captain and his team of scuba divers behind with a dwindling supply of oxygen in their tanks.
Don Megowan
as Captain Fathom
Richard H. Cutting
as Professor Barclay
Barbara Wilson
as Carol Barclay
Kenneth Tobey
as Jack Clyde
Rod Williams
as Derek Taylor
David McMahon
as Duncan
Robert Sampson
as Gordon
David McLean
as Seaman Duncan
