Atlanta is captured by an undersea race when Stingray investigates the collapse of an oil drilling rig. She discovers that the creatures only attacked the rig out of self-defence, believing that their home was under attack. Unfortunately, a bomb has been planted aboard Stingray that will explode when the ship dives. Atlanta makes a desperate effort to contact Stingray but, fortunately, Marina's pet seal, Oink, discovers the bomb and pushes it off in time