Producer Roger Corman got the idea for the movie while reading a Los Angeles Times article about a one-man submarine manufactured by Aerojet General. He phoned them and asked them if he could use it in a film, telling them that he couldn't pay them but they'd get free publicity. According to Corman they were delighted.
Besides serving as producer, Roger Corman also drove the camera and equipment truck.
Film debut of Jonathan Haze; he was working at a gas station at the time he did this movie and had to grow a mustache for his role as Joe.
The original title was to be "It Stalked the Ocean Floor," but the distributors objected on the grounds it was "too cerebral."
The first film produced by Roger Corman.
Principal photography took six days, with two additional days for the underwater scenes.
Stuart Wade came up with the idea to sing a song in the movie.