The Inferno Island Boat is a vehicle that was only seen in the episode "The Inmates of Summer."
The Inferno Island Boat is a large boat made of metal that is brown in color. There is barbed wire around some parts of the boat and it has barred windows.
The Inferno Island Boat comes shortly after the Sun-N-Fun Boat leaves for its destination. SpongeBob and Patrick unknowingly board this boat thinking it is the one heading for Sun-N-Fun Island. They are "greeted" by the Warden who sees SpongeBob and Patrick as nothing but criminals. The boat then departs for Inferno Island.