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.
The original title was to be "It Stalked the Ocean Floor," but the distributors objected on the grounds it was "too cerebral."
The very first film produced by Roger Corman.