Helmsman

A Helmsman is a person who steers a ship and many types of boats. In the merchant Marine, this is usually an able seaman. In the Marines, it is a seaman or a quartermaster.

In the Series
In the series, the only known helmsman of any crew is Jesus Burgess of the Blackbeard Pirates. It is unknown if Burgess is still a helmsman, as he was promoted to captain of the Blackbeard Pirates' first ship somewhere around the time Blackbeard became one of the Yonko.

The Straw Hat Pirates do not have an official helmsman, though the most common people seen steering the ship is either Nami, Usopp, or Chopper in his human form. However, Franky and Sanji have also been seen steering the Thousand Sunny many times. Jinbe also has some skill at steering a ship.