This horror film concerns a shipwrecked yachting party. Rose (Brooke Adams) and her fellow yacht-mates, including the captain (John Carradine) run aground on an island when they hit an odd-looking freighter. Once beached, they meet up with an aging SS Commander (Peter Cushing) who had been in charge of a crew of zombies.
This is not meant as a comment on the quality of the men under him, they were real zombies. Since the zombies were taken from the ranks of murderers and other miscreants, they were not activated and the SS Commander sunk them with his submarine. Now they are rising up from the depths to create mayhem among the stranded members of the yachting party.