This Republic "special" stars Rod Cameron as deep-sea diver Gunner McNeil.

When his partner (James Brown) drowns under mysterious circumstances, McNeil investigates, all the while carrying out a salvage assignment for the lovely Suntan Radford (Adele Mara).

The titular Sea Hornet is a vessel which was sunk during wartime while carrying a fortune in gold.

Someone is willing to commit murder to claim the treasure for his (or her) own: is it Suntan, or second lead Ginger (Adrian Booth), or the disreputable-looking Johnny Radford (Richard Jaeckel), or even Gunner's first made Swede (Chill Wills)?

Sea Hornet is capped by a thrill-packed action finale, in the fine tradition of Republic studios.