Pirates of the High Seas (Pirates of the High Seas - Phantom Raiders of the Deep) (1950)

Adventurer Jeff Drake sails to a Pacific island in aid of Kelly Walsh, an old friend whose freight line is being sabotaged by a ghost ship (such as the classic Flying Dutchman). Drake and Walsh's investigation concerns the search for Walter Castell, an escaped convict who stole 5 million dollars in diamonds at the close of World War II. Several other people, including Walsh's sister, all want to go to the island. Drake and his friends encounter multiple dangers when they are attacked by a gang also looking for the stolen diamonds led by the mysterious 'Admiral'...