Creature from the Black Lagoon (1954) on Netflix

After Dr. Carl Maia finds unique skeletal remains, a group of scientists led by David Reed head down the Amazon to see if other remains can be found. They have little luck at first until hearing that further downriver lies the Black Lagoon where other fossils might be found. They get more than they bargained for when they discover a living prehistoric creature - a half-man, half amphibious reptile - that doesn't take kindly to their attempts to capture him. The creature takes a liking to Kay Lawrence and kidnaps her but goes to war against the scientists and won't let them leave the lagoon.