Atlantis is an episode of Venturian Battle.
The movie opens up on a large with Athansios talking to Prisco about a fish he claims exists but no one has been able to find it. After the crew is gathered (which required awaking Terrence and Scottie), Boyce explains their mission.
Boyce discusses how a vanished sea station built for a theory of his that the mythical city of Atlantis existed, was swallowed up by the ocean. He then presents a pyramid he claims is the map to Atlantis, but Robert Jacob refuses to help look, persisting that they are a salvage adventure that just picks up as much treasure as they can. Before Boyce can convince him, however, the ship makes contact with a Monster Crab that sends their ship plummeting to the sea floor. Upon discovering a sub from the lost sea station, the Captain goes on a scuba mission to deal with the crustacean. After blasting apart the crab, the Tyler discovers a crystal on the ocean floor and retrieves it. After Terrence's refusal to fix the cable, the ship goes off a cliff.
The ship plumets into an aquatic volcano, but makes its way through the deep, subterranean magma tunnels into a depth thought not to exist. Excitedly, Boyce says that once all the crystals were found, the location of Atlantis will be clear. Observing the wreck of their current sub, the team quickly builds new ones, the Typhoon Turbo Sub and the Seabed Scavenger with which to find the crystals. The two newly built subs, Robert's personal vehicle, the Wreck Raider, and Terrence and Tyler in diving suits alongside move out, but not before a strange, green, octopus decides to follow.
The convoy of submarines go deep within the ocean, but Scottie stops them upon the discovery of the mysterious squid temple. The divers are soon met by several, red Squid warriors, and Prisco suggests to let them know the divers mean no harm. To his horror, Scottie reads a sign on the temple warning those who enter, and so after taking a photo of the Squids, Prisco swims away. After a respite, the crew is met by a Giant Squid. Thinking quickly, they are able to impale the squid's tentacles on sharp rock, and the second crystal is discovered. The subs soon see odd things moving in the sand, which Robert says are Manta Rays and completely harmless. However, as Manta Warriors gather, Terrence thinks twice about this statement.
The Manta Warriors continue to surround the submarines, but they disperse. Tyler credits this to his Kung Fu, but they soon discover it is because of a big threat: an enormous black shark. After an attemps to get rid of the shark fails, Robert finally kills him by sending a dummy diver (which is a napalm canister with a helmet) to lure him away. When the shark eats the fake diver as is about to eat Robert when the creature farts and suddenly explodes apart. Shark parts hover away amidst white blood. The third crystal, a talisman, is found, but just as Robert picks it up, a Manta Warrior erupts from the sand and takes it from him. Robert goes after the Manta Warrior on his own in the Wreck Raider, but the rest of the crew finds him (with the talisman) using the tracking device that all vehicles have. Unfortunately, their happiness is ended abruptly when Shark Warriors come out of a large, stone shark door to a mysterious structure. The crew gets several tridents and wedge them in the throttle lever causing their vehicles to drive away, followed closely by the swarming Shark Warriors.
After hiding from the sharks in the sand, Terrence sees the last crystal, but is depressed when there is no Atlantis. After reassurance from Tyler, Terrence learns that crystals are the keys to Atlantis, and he inserts them in the correct places on the portal. After all the keys are placed, Athansios discovers one is still missing, but that problem is solved when the triangle unfolds to reveal the final key. When this key is placed, the sea shakes and rumbles, and the rock shark statues on either side of the Portal become alive. A Portal forms between all the keys, and the crew decides to build a rocket out of the Wreck Raider using their oxygen tanks to get past the newly-created sharks. They rocket into the portal, and the large, beautiful, golden city of Atlantis awaits for them on the other side. In the following newspaper article, it is seen that Prisco discovers the fish he was looking for!
Meanwhile, Robert uses a teleporter to teleport the Atlantis portal to his portal room, which he locks away from anybody but him and Brendan, and Cyan recaps the adventure to a group of tourists in Robert's Abode.