The Wreck of the Mauna Loa Amusement Park Ride was a hidden replica of the real Mauna Loa. It made its only appearance in the episode "The Wreck of the Mauna Loa."
Its early history is unknown. It was built to act as an amusement park ride. Later the ship's existence became sealed and unknown to the rest of the world until SpongeBob and Patrick came.
Once the duo found it, they made it their secret hideout. Although Patrick spread the Mauna Loa's evidence of existence, SpongeBob eventually grew Mr. Krabs's suspicion and made him follow the two to their hideout. SpongeBob had no choice but to allow the treasure-hunting crustacean to enter the hideout. Mr. Krabs found out that the treasure was just tokens, the pirates are plastic, and the fact indicating the ship was actually a park ride. Suddenly instead of finding treasure, he converted the ship back into an amusement park ride. But the ride wasn't safe, causing it to break. The police closed it down, and everyone had to leave the "hideout."
Ironically, there was another ship, the actual Mauna Loa. SpongeBob asked Patrick if he could keep this a secret from everyone else, and Patrick said no.