Screamers

In 1891, a boat transporting prisoners to Cayenne sinks in the sea of West Indies. The doctor on board, Claude le Ross, and four other survivors succeed in joining an island. Two men are savagely slaughtered. Claude and his companions arrive in a cemetery, among a group of natives lead by a superstitious despot, Edmond Rackham. He is accompanied by a servile young woman, Amanda. Soon, Claude's two friends disappear in strange circumstances, after having been invited by the master of the island. Claude discovers that Rackham retains captive a biologist, Ernest Marvin, Amanda's father. He is now in charge of maintaining alive the old Marvin, very sick, in order that Rackham could continue his hunting for a treasure... Furthermore, the scientist has created mutants, half men, half fish, capable to swim to important depths, because it is under the island that is found the city of Atlantis, that was gobbled with all its wealth...