Flag of the United States Merchant Marine
Captains, mates (officers), and pilots supervise ship operations on domestic waterways and the high seas. A captain (master) is in overall command of a vessel, and supervises the work of other officers and crew. A captain has the ability to take the conn from a mate or pilot at any time he feels the need. On smaller vessels the captain may be a regular watch-stander, similar to a mate, directly controlling the vessel's position. Captains and department heads ensure that proper procedures and safety practices are followed, ensure that machinery is in good working order, and oversee the loading and discharging of cargo and passengers. Captains directly communicate with the company or command (MSC), and are overall responsible for cargo, various logs, ship's documents, credentials, efforts at controlling pollution and passengers carried.
Mates direct a ship's routine operation for the captain during work shifts, which are called watches. Mates stand watch for specified periods, usually in three duty sections, with four hours on watch and eight hours off. When on a navigational watch, mates direct a bridge team by conning, directing courses through the helmsman and speed through the lee helmsman (or directly in open ocean). When more than one mate is necessary aboard a ship, they typically are designated chief mate or first mate, second mate and third mate. In addition to watch standers, mates directly supervise the ship's crew, and are assigned other tasks. The chief mate is usually in charge of cargo, stability and the deck crew, the second mate in charge of navigation plans and updates and the third mate as the safety officer. They also monitor and direct deck crew operations, such as directing line handlers during moorings, and anchorings, monitor cargo operations and supervise crew members engaged in maintenance and the vessel's upkeep.
Harbor pilots guide ships in and out of confined waterways, such as harbors, where a familiarity with local conditions is of prime importance. Harbor pilots are generally independent contractors who accompany vessels while they enter or leave port, and may pilot many ships in a single day.
Engine officers, or engineers, operate, maintain, and repair engines, boilers, generators, pumps, and other machinery. Merchant marine vessels usually have four engine officers: a chief engineer and a first, second, and third assistant engineer. On many ships, Assistant Engineers stand periodic watches, overseeing the safe operation of engines and other machinery. However, most modern ships sailing today utilize unmanned machinery space (UMS) automation technology, and Assistant Engineers are dayworkers. At night and during meals and breaks, the engine room is unmanned and machinery alarms are answered by the Duty Engineer.
Marine oilers and more experienced qualified members of the engine department, or QMEDs, maintain the vessel in proper running order in the engine spaces below decks, under the direction of the ship's engine officers. These workers lubricate gears, shafts, bearings, and other moving parts of engines and motors; read pressure and temperature gauges, record data and sometimes assist with repairs and adjust machinery. Wipers are the entry-level workers in the engine room, holding a position similar to that of ordinary seamen of the deck crew. They clean and paint the engine room and its equipment and assist the others in maintenance and repair work. With more experience, they become oilers and firemen.
United States Merchant Marine officer's crest
Able seamen and ordinary seamen operate the vessel and its deck equipment under officer supervision and keep their assigned areas in good order. They watch for other vessels and obstructions in the ship's path, as well as for navigational aids such as buoys and lighthouses. They also steer the ship, measure water depth in shallow water, and maintain and operate deck equipment such as lifeboats, anchors, and cargo-handling gear. On tankers, mariners designated as pumpmen hook up hoses, operate pumps, and clean tanks. When arriving at or leaving a dock, they handle the mooring lines. Seamen also perform routine maintenance chores, such as repairing lines, chipping rust, and painting and cleaning decks. On larger vessels, a boatswain—or head seaman—will supervise the work.
As of 2011, a typical deep-sea merchant ship has a captain, three mates, a chief engineer and three assistant engineers, plus six or more unlicensed seamen, such as able seamen, oilers, QMEDs, and cooks or food handlers known as stewards. Other unlicensed positions on a large ship may include electricians and machinery mechanics.