Students dressed in deep sea helmets travel to the ocean deep in a yellow school-bus submarine. When they get there, they frolic with fish, chase luminescent squid, and discover an old shipwreck. But when it’s time to return to the submarine bus, one student lingers to take a photo of a treasure chest and falls into a deep ravine. Luckily, the child makes an unexpected friend - a maybe-not-so-extinct sea creature called a Pleiosaur- that’s happy to entertain the young explorer until the teacher returns.