Captain Nemo and his starving crew go ashore on a seemingly deserted island in search of food. When Blaster goes missing, Nemo and Humility embark on a daring rescue mission but soon encounter a giant electric eel.

The underwater volcanoes turn out to reveal a clue to the legendary underwater city of Atlantis. A small group goes exploring and finds what appears to be an ancient outpost of the lost civilization, but also realizes that it is home to terrifying sea lilies and the crew must fight for their lives.