It Came from Beneath the Sea

During the submarine's shakedown in the Pacific, the crew detects a massive sonar return that dwarfs anything they've seen. Unable to outrun or maneuver away, the submarine is disabled but eventually frees itself and returns to Pearl Harbor. Tissue from a huge sea creature is discovered jammed in the dive planes, hinting at a mysterious threat.

Joyce and Carter are summoned to identify the strange tissue. They determine it is a small part of a gigantic octopus. Their finding challenges official skepticism and sets the stage for a possible sea monster threat.

Military officials remain skeptical, but reports of missing swimmers and ships pull the threat into the public eye. Joyce and Carter argue the giant is from the Mindanao Deep and was driven out by hydrogen bomb testing, making it radioactive and more dangerous.

A Canadian freighter is attacked; survivors reach a life raft and are questioned by psychiatrists. Joyce persuades the first sailor to repeat what he saw, confirming a creature with giant tentacles.

The U.S. government halts sea traffic in the North Pacific to prevent further losses. Carter flies out to trace a missing ship while Mathews and Joyce follow up on reports of five missing people off the Oregon coast.

Sheriff Bill Nash takes Mathews and Joyce to the attack site, where giant suction cup imprints dot the beach. The case deepens their romantic bond as they decide to bring Carter into the effort.

Nash is attacked by the giant octopus, and the scientists barely escape as the creature threatens the shore. In response, authorities hasten plans to mine Pacific coast waters to trap it.

An electrified safety net is strung across the entrance to San Francisco Bay, while Carter flies along the shoreline to bait the sea with dead sharks from a helicopter. Joyce unveils a jet propelled atomic torpedo in hopes of driving the monster back into open sea for a final strike.

The creature demolishes the underwater net and heads toward San Francisco. The Navy orders the Golden Gate Bridge abandoned as the electric circuit powering the net remains on, irritating the monster.

The giant grabs the bridge and destroys Carter's car, escalating the panic in the city. Mathews rushes to Carter and then to safety as another bridge segment collapses under its force.

San Francisco residents panic and flee while the Navy struggles to evacuate the Embarcadero and Ferry Building. Government officials authorize Mathews to take out the submarine with the torpedo, with Carter joining the mission and Joyce remaining at the base.

Flamethrowers drive the tentacles back into the sea and Mathews fires the jet torpedo. The octopus seizes the submarine, and Mathews uses an aqualung to place explosive charges before being knocked out. Carter swims out, shoots one eye, and forces the monster to release the sub. The torpedo detonates, destroying the octopus.

The three celebrate at a restaurant after the battle, savoring their survival and the team's bond. Mathews then makes an impromptu proposal to Joyce, and she accepts.