They also maintain logs and other records of ships' movements and cargo carried. On large vessels, captains are assisted by deck officers or mates. Merchant marine vessels those carrying cargo overseas have a chief or first mate, a second mate, and a third mate. Mates oversee the operation of the vessel, or stand watch for specified periods, usually 4 hours on and 8 off. Engineers or marine engineers operate, maintain, and repair propulsion engines, boilers, generators, pumps, and other machinery.
Assistant engineers stand periodic watches, overseeing the operation of engines and machinery.
Seamen, also called deckhands, particularly on inland waters, operate the vessel and its deck equipment under the direction of the ship's officers, and keep the nonengineering areas in good condition. They stand watch, looking out for other vessels, obstructions in the ship's path, and aids to navigation. They also steer the ship, measure water depth in shallow water, and maintain and operate deck equipment such as life boats, anchors, and cargohandling gear. When docking or departing, they handle lines. They also perform maintenance chores such as repairing lines, chipping rust, and painting and cleaning decks and other areas.