Nami is the crew's navigator, who guides the ship using an abundance of sailing knowledge and an innate ability to read the weather. The crew can't get very far at sea, without her. She's been adept at making sea charts since she was young, and her dream is to one day make a map of the world. She really hated pirates, because her village was controlled by some of them, but she joined Luffy's crew after he saved her.
With her levelheaded personality, Nami doesn't just direct the ship, she also manages the many fools onboard. She's especially strict when it comes to money, so she frequently cracks down on her many crewmates who waste it.