Treasure hunters face the dangers of the deep in Underwater!, RKO's romantic action-adventure set in the exotic undersea world of the Caribbean. Hollywood beauty Jane Russell is Theresa, girlfriend of ship operator Johnny, who teams up with perennial rainbow chaser Dominic. They hunt for fabled treasure lost in an old Spanish galleon off the Cuban coast. Amid the threat of rapacious sharks and the hazards of underwater salvaging, the adventurers work against time. They must raise the gold from its ghostly grave before the rotting old ship's hull slips off the ledge where it has rested for centuries. If that weren't enough, the group must also outwit a local pirate. This thriller is photographed in Technicolor in a beautiful setting of lush tropical ports and unfathomable undersea locations. - Two men and woman dive for treasure ship.