Sunken Ghost Ship

A wrecked ship that serves as a gate to the Valley of Bowser, after defeating Wendy O. Koopa Mario has to swim through this ship in order to make the doorway to World 7 come out of the sea. On board the ship are some Bill Blasters, Floating Mines, Koopas, and a massive swarm of Disappearing Boo Buddies.

It's one of the Koopa Kids Air Ships from Super Mario Bros. 3. Probably Larry's because his castle is in the Valley of Bowser.