"The Monster from the Lost Lagoon!"
The Fantastic Four investigate a sea monster sighting and strange reports of ships sinking. Reed, Johnny and Ben search around and team up with an aqua specialist from the local marina to find the monster. But the specialist tries to kill the other three on a diving expedition as they learn that the sea monster is actually a creature from outer space who was stranded on Earth and trying to repair his ship. The FF watch as the creature finishes his repairs and returns to the stars.