An able seaman (AB) is a seaman and member of the deck department of a merchant ship with more than two years' experience at sea and considered "well acquainted with his duty". An AB may work as a watchstander, a day worker, or a combination of these roles. Once a sufficient amount of sea time is acquired, then the AB can apply to take a series of courses/examinations to become certified as an officer. At sea an AB watchstander's duties include standing watch as helmsman and lookout. A helmsman is required to maintain a steady course, properly execute all rudder orders and communicate using navigational terms relating to heading and steering. A watchstander may be called upon to stand security-related watches, such as a gangway watch or anchor watch while the ship is not underway.
