Ray Harryhausen purchased the model for the ship that the octopus sinks from a five and dime store.
The submarine scenes were shot in an actual submarine in Long Beach, California.
Because the budget was so low, Ray Harryhausen saved money by building his octopus model with six rather than the correct eight tentacles. He tried to pose the creature so this lack of the right number of arms wasn't apparent.
This is the film that brought together producer Charles H. Schneer and special effects legend Ray Harryhausen. Their professional relationship would last until Clash of the Titans (1981), the final feature for both men.
City officials refused to allow the filmmakers to shoot on the real Golden Gate Bridge, because they didn't want the public to think that the bridge could actually fall. Ray Harryhausen recreated the entire bridge in miniature.
The "atom-powered" submarine shown cruising on the surface is actually the diesel-electric submarine USS Cubera (SS-347).
The Special Jet Propelled Torpedo is actually an aerial torpedo (it was delivered by aircraft and by torpedo boats) that had its propellers and rudders removed.
Ray Harryhausen's father built the metal armature for the model for the octopus.
Most of the scenes in this film were done in a single take.
The car miniatures and the Golden Gate Bridge miniature were both made out of lead.
Several subs appear in stock footage. The jet-propelled torpedo gets loaded onto a real sub that appears to have a fake conning tower, probably built over the real conning tower to make this sub visually match the sub that appears later. It's hard to read the sub's number in the torpedo-load scene, but it appears to be 334 --USS Cabezon. The Cabezon arrived in California in 1953 to join the reserve fleet and might have been undergoing inactivation when the film crews set up.
Columbia booked this as a double bill with Creature with the Atom Brain (1955) all across the US.
When the Navy first uses depth charges on the octopus, the destroyer most prominently featured is DD-540, which is the USS Twining. Launched in 1943, the Twining won many battle stars for action in World War II and in Korea. She was sold to the Republic of China in 1971 and stricken in 1999.
Early in the film Kenneth Tobey walks right past a "No Smoking" whilst smoking a cigarette in the marine biology lab.
The background plates for the Golden Gate Bridge were shot without permits.
Donald Curtis cited this film as his personal favorite among the films he starred in.
Opening credits: The characters and incidents portrayed and the names used herein are fictitious and any similarity to the name, character or history of any person is entirely accidental and unintentional.