The gill-man, riddled with bullets at the end of Creature from the Black Lagoon, has survived in the Amazon River. Captain Lucas (Nestor Paiva) again sails up a tributary with George Johnson (Robert Williams) and Joe Hayes (John Bromfield) to capture it again. Lucas points out that the previous expedition killed five people. The creature attacks Joe and is driven off. They finally capture it when explosives render it unconscious.
The creature is sent to the Ocean Harbor Oceanarium in Florida, where it is studied by animal psychologist Professor Clete Ferguson (John Agar) and ichthyology student Helen Robson (Lori Nelson). Helen and Clete are falling in love, much to the disgust of Joe Hayes. The gill-man too is attracted to her, which makes it difficult to communicate with the creature. It is chained up and displayed to the public, like King Kong, and subjected to electric shocks. By the time it escapes from captivity, killing Joe in the process, the audience is pretty much on the creature’s side. It ignores the screaming crowds and heads for the ocean.
But it returns for Helen, stalking her and Clete. The creature abducts her from a restaurant during a party, so she can wear a slinky gown as she is carried off unconscious. Cleve chases it but it escapes into the sea with her. Two men find Helen unconscious on the beach and it kills them and takes Helen away again. Next time they emerge from the sea, Clete and the police arrive and when it surfaces, the police shoot it dead and Clete saves Helen.
The film was produced by William Alland and directed by Jack Arnold, as was the first film, from a screenplay by Martin Berkeley. It was largely dismissed by critics, though the underwater photography got some respect. It was filmed in Marineland and in the St. Johns River in Florida, the only film made in 3D in 1955. The creature was played by Tom Hennesy on land and again by Ricou Browning underwater. Ginger Stanley did underwater stunt work as she did in the first film. Hennesy almost drowned when he dove into a raft of jellyfish with her. She escaped, but he was trapped in his waterlogged costume. Two local boys, who had been watching the filming from their boat, dragged him out. Browning was not considered threatening enough to play the creature out of the water, as he was only six-foot-one. Also appearing was an incredibly young Clint Eastwood in a white lab coat as lab technician Jennings.