Around the beginning of the 20th century, British archaeologist Professor Aitken and his son, Charles, have chartered a ship called the ''Texas Rose'' to take them out to sea, where they plan to dive underwater in a diving bell designed by engineer Greg Collinson. Although everyone aboard the ship, including Greg, thinks that the Professors Aitken are just going to look at fish, Charles and his father are secretly searching for proof of the existence of the lost city of Atlantis. He and Greg find it on their first dive, but are attacked by a reptilian sea monster, which comes through the bottom of the diving bell, but Greg is able to fend it off by sticking a live wire into its mouth, electrocuting it.