One Piece: The Giant Mechanical Soldier of Karakuri Castle

The StrawHat crew salvage a treasure chest from a sinking wreckage during a raging storm, but it turns out to be an old lady hiding inside it. To get the Straw Hat Pirates to take her home, she promises them the treasure of a golden
The Straw Hats visits an island, known as Mecha Island, where a fisherman sings an old folk song about a Golden Crown. Searching for that mysterious treasure, they find a hidden entrance into the island. The island's leader, Ratchet, impressed with the find and in search of the Golden Crown himself, invites the crew to join him in his search and the crew along with Ratchet and his henchmen enter the cave. As it turns out, the islands true form, is that of a giant turtle. Ratchet, who had known this all along, uses his mechanical castle to take control of the turtle, in order to use it, to take over the world. Now the Straw Hats have to stop not only Ratchet, but also the helpless turtle, from crashing into a nearby island.