Nautilus is the only Navy Ship in the big harbour and has the number 114 on his sides.
He lives near the institute of oceanography. Nautilus was first seen being docked by Theodore and George, when George wanted to be a navy ship too. His second appearance was his starring role, as he was in charge of saving Canso Colossus the king of super tankers, who was sinking. Theodore and the tugboats seem to look up to him a lot. Besides being one of the sleekest and fastest boats in the Big Harbour, Nautilus also has a big heart and always comes to the aid of any boat.
- Nautilus is possibly based off a destroyer.