Thanks to hydrogen bombs, a radioactive and hungry octopus of gigantic proportions raises to surface to hunt the easiest prey of them all: Man.
IT CRUSHES! KILLS! DESTROYS!
- Artistic License – Biology: Due to the low budget, Harryhausen gave the octopus only six tentacles.
- Big Bad: The giant octopus rampaging across the sea.
- Event Title
- Fire-Breathing Weapon: A trio of marines with flamethrowers is dispatched to drive the octopus back to the sea when it attempts haul itself into San Francisco.
- Giant Eye of Doom: To make it let go of their submarine, Dr. Carter has to swim close to one of the octopus's eyes and attack it.
- Monumental Damage: The Golden Gate bridge gets thrashed by the octopus.
- Nuclear Mutant: While the radiation didn't create the giant octopus, it however made it desperate enough to come up from the depths to be able to feed itself.
- The Real Heroes: Listening to a radio broadcast that is congratulating "the unsung heroes" of the attack on San Francisco, our protagonists raise their glasses in anticipation, only to hear that the broadcast is referring to civilian defense volunteers, the crossing guards and the street railway employees.
- Screaming Woman: Prof. Joyce starts screaming as she sees the octopus in all of its glory for the first time.
- Sensor Suspense: The octopus's first attack is depicted through submarine sonar and geiger counters.
- Show Some Leg: Prof. Joyce uses her feminine charm to make reluctant Seaman Hall tell about the giant octopus attacking his ship.
- Tentacled Terror: The titular "it" that came from beneath the sea is a giant octopus.