Helmsman
From One Piece Encyclopedia
A helmsman is a person who steers a ship and many types of boat. In the merchant marine this is usually an able seaman. In the Marines it is a seaman or a quartermaster.
In One Piece, the only known helmsman of any crew is Jesus Burgess of the Blackbeard Pirates. The Straw Hat Pirates do not have an official helmsman, though the most common person seen steering the ship is either Nami or Tony Tony Chopper in his human form. However Franky has been seen steering the Thousand Sunny many times.
