The Creature Walks Among Us (1956) on Netflix

The wealthy Dr. William Barton organizes an expedition to the Florida Everglades with the scientists Dr. Thomas Morgan, Dr. Borg and Dr. Johnson to capture the Creature. They navigate in the ship of Capt. Stanley with Jed Grant and Dr. Barton's wife Marcia Barton joins the team. Dr. Barton is paranoid with the jealousy of Marcia and Jed is harassing her in the trip. They chase and capture the Creature that is totally burnt. Without breathing through the gills, the Creature is turned into an air breather through his hidden lungs and brought to the ranch of Dr. Barton in California. Dr. Morgan defends the thesis that the Creature responds to the way that he is treated and asks people to be not violent with him. But Dr. Barton is near a breakdown with his jealousy of Marcia.