Gerald Clamson (Lewis) is a bank examiner who loves fishing on his annual two-week holiday. Unfortunately, one day at the ocean he reels in Syd Valentine (also played by Lewis), an injured gangster in a scuba diving suit. Syd tells Gerald about diamonds he has stolen from the other gangsters and hands him a map. Gerald escapes as frogmen from a yacht machine-gun the beach. They swim ashore, locate Syd and gun him down. Their leader Thor (Harold J. Stone) ensures Syd's demise by firing a torpedo from his yacht that goes ashore, blowing a crater into the beach.