One of the only films produced in Stereo-Vision, a short-lived process which combined widescreen, similar to CinemaScope or Panavision, and 3D.
The actual movie's opening credits lists only one director, Byron Haskin, which makes Paul Stader uncredited as director but he is credited as filming the underwater sequences, which is basically what 2nd Unit Directors do on films. The directing credit is still given to the main director.
Writer W.R. Burnett is known for Film Noir adventures like High Sierra. This film fits under the category of Neo Noir adventure, and also resembles Treasure of the Sierra Madre on how crazy treasure makes certain people.
Directed by Byron Haskin who directed WAR OF THE WORLDS, which was supposed to be partially 3D like this film is completely.
Filmed in cala d'or, in Mallorca, Spain, although the movie was never released in Spain.