Ol' Ironsides is a former ship that makes its only appearance in the episode, "Karate Star."
"Ol' Ironsides" is posted on one of the sides of the boat. It is displayed in a bluish color from an angle, yet when the camera shows a close up of SpongeBob, it appears to be along the lines of a purple color. A steamer appears at the top of the boat, which shows that it may have been a steamer boat.
The name may reveal that the material used to make the boat was iron. There are two visible windows on the front and right side of the steering room. The screws used to construct the boat are clearly visible.
Once Patrick chops the boat in half, the inside can be clearly seen. Wooden walls and flooring can be depicted after this process, yet no furnishing or decorations appear in the boat. The floor of the steering room is not visible due to it being on a higher level. The inside does show signs of aging, showing it is an older steamer boat than others that have appeared.
This ship is inspected by SpongeBob to be "solid as a rock." After what SpongeBob assumes to be a failure when Patrick chops it, the boat begins to wobble and, finally, snaps into two large pieces. It is unknown if this boat is from the surface or an abandoned undersea steamer boat.
Old Ironsides was actually the nickname of an American frigate used to fight in the War of 1812.
In the episode "Sanctuary!," SpongeBob adopts a snail named, "Old Ironsides."