Creature from the Black Lagoon (1954)

Creature from the Black Lagoon is a monster horror film directed by Jack Arnold, and starring Richard Carlson, Julia Adams, Richard Denning, Antonio Moreno, and Whit Bissell. The eponymous creature was played by Ben Chapman on land and Ricou Browning in underwater scenes.

Synopsis
A geology expedition in the Amazon uncovers fossilized evidence from the Devonian period of a link between land and sea animals in the form of a skeletal hand with webbed fingers. Expedition leader Dr. Carl Maia visits his friend, Dr. David Reed, an ichthyologist who works at a marine biology institute. Reed persuades the institute's financial backer, Dr. Mark Williams, to fund a return expedition to the Amazon to look for the remainder of the skeleton.

They go aboard a tramp steamer, the Rita, which is captained by a crusty old codger named Lucas. The expedition consists of David, Carl and Mark, as well as Reed's girlfriend, Kay Lawrence, and another scientist, Dr. Edwin Thompson. When they arrive at the camp, they discover that Maia's entire research team has been mysteriously killed while he was away. Lucas suggests it was done by a jaguar, but the others are unsure. In fact, the camp was attacked by a piscine amphibious humanoid, a living member of the same species from which the fossil originated. The creature, curious upon seeing the expedition, investigates the camp site, but when its sudden appearance frightens the members, they attack it, and in response, the enraged creature kills them.

The excavation of the area where Carl found the hand turns up nothing. Mark is ready to give up the search, but David suggests that perhaps thousands of years ago the part of the embankment containing the rest of the skeleton fell into the water and was washed downriver. Lucas says that the tributary empties into a lagoon known as the "Black Lagoon", a paradise from which no one has ever returned. The scientists decide to risk it, unaware that the amphibious "Gill Man" that killed Carl's assistants earlier has been watching them. Taking notice of the beautiful Kay, it follows the Rita all the way downriver to the Black Lagoon. Once the expedition arrives, David and Mark go diving to collect fossils from the lagoon floor. After they return, Kay goes swimming and is stalked underwater by the creature, who then gets briefly caught in one of the ship's draglines. Although it escapes, it leaves behind a claw in the net, revealing its existence to the scientists.

Subsequent encounters with the Gill-man claim the lives of two of Lucas's crew members, before the Gill-man is captured and locked in a cage on board the Rita. It escapes during the night and attacks Edwin, who was guarding it. Kay hits the beast with a lantern; driving it off before it can kill Edwin. Following this incident, David decides they should return to civilization, but as the Rita tries to leave, they find the entrance blocked by fallen logs, courtesy of the escaped Gill-man.

While the others attempt to remove the logs, Mark is mauled to death trying to capture the creature single-handedly underwater. The creature then abducts Kay and takes her to his cavern lair. David, Lucas, and Carl give chase to save her. Kay is rescued and the creature is riddled with bullets before he retreats to the lagoon where his body sinks in the watery depths, presumably dead.