Monster From The Ocean Floor (1954)

aka’s: It Stalked The Ocean Floor/
It Stalked The Monster Floor

Julie Blair (Anne Kimbell), an American on vacation in Mexico, spots a giant, one-eyed amoeba rising from the ocean, but when she tries to tell the authorities, no one believes her. She finally teams up with a marine biologist (Stuart Wade) in an attempt to destroy it. Also stars Dick Pinner.