The Wreck of the Mauna Loa Amusement Park Ride was a hidden replica of the real Mauna Loa. Its only appearance is 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 come.
Once the duo find it, they make it their secret hideout. Although Patrick spreads the Mauna Loa's evidence of existence, SpongeBob eventually draws Mr. Krabs' suspicion and makes him follow the two to their hideout. SpongeBob has no choice but to allow the treasure-hunting crustacean to enter the hideout. Mr. Krabs finds out that the treasure is just tokens, the pirates are plastic, and the fact indicating the ship is actually a park ride. Suddenly, instead of finding treasure, he converts the ship back into an amusement park ride, but the ride is not safe, causing it to break. The police close it down, and everyone has to leave the "hideout."
Ironically, there was another ship, the actual Mauna Loa. SpongeBob asks Patrick if he can keep this a secret from everyone else, and Patrick says no.