BEYOND ATLANTIS

A man brings a woman named Syrene (Leigh Christian) to an island, and she pays him with some pearls. The inhabitants of the island appear to be inbred, with oversized eyes, and they kill an intruder that they find.

Back on the mainland, the fisherman Manuel the Barracuda (Vic Díaz), pays East Eddie (Sid Haig), who runs the piers, with some pearls. Eddie shows them to Logan (Ashley), a local hustler, and they decide to find the source of the pearls. Logan meets Vic Mathias (Patrick Wayne), who has a boat, and strikes a deal with him to use the boat to look for the pearls.

Dr. Katherine Vernon (Lenore Stevens) overhears this and talks to Logan, who agrees to meet her the next day. At a museum, Dr. Vernon tells Logan that she wants to find the pearls solely for their scientific value.

The party sets off for the island, confronting Manuel the Barracuda and finding the location. The group encounters Syrene and her people, who can live both on land and in the sea, and she agrees to show the party where the pearls are, but Syrene and her father Nereus (George Nader), want to mate Syrene with one of the group; specifically, Vic. She leads them to beds of pearls and the first mate is mysteriously killed. Vic wants to leave, but Logan and Eddie want to make one more dive. Syrene enraptures Vic and they mate.

Nereus decides that the group must die, and Vic, Logan, Eddie and the crew have to fight their way back to their boat. Katherine is jumped by Syrene, but Syrene is killed, thus ending any chance for the race of sea people to continue. They all march into the sea as Logan takes a blanket of pearls from Syrene's funeral pyre. Manuel arrives and tries to double-cross the surviving pearl hunters. A fight breaks out and the case of pearls falls overboard, with Logan trying to convince Eddie and Vic that they can find the pearls again.