A Bone Boat is a type of raft that appears in New Super Mario Bros. 2. Mario (or Luigi) use these to cross lava caverns. They look like Bonecoasters only thicker and they also move slower. They act like Skull Rafts from Super Mario World.
Bone Boats appear in New Super Mario Bros. 2. Two Bone Boats appear in World 6-2, where they sail along the lava. Once a Bone Boat has reached its stop, Mario or Luigi can ground pound its head to make it spit out a large amount of coins, or even a 1-Up Mushroom. A minor detail: the eyes glow every time a vocal riff (the "Bah" sound) was heard. Bone Boats are also featured on Course 3 of the Platform Panic Pack in the game's downloadable Coin Rush course packs. Bone Boats also appear in Course 3 of the Coin Challenge C DLC, although they were noticably missing the characteristic head.