Apprentice mate (steersman) of towing vessels: a mariner qualified to perform watchkeeping on the bridge, aboard a towing vessel, while in training under the direct supervision of a licensed master or mate (pilot) of towing vessels.
Assistant engineer: a qualified officer in the engine department.
Ballast control operator (BCO): a licensed officer restricted to service on MODUs. The duties involve the operation of the complex ballast system found on many MODUs. A ballast control operator, when assigned to a MODU, is the equivalent of a conventionally licensed mate.
Barge supervisor (BS): a licensed officer restricted to service on MODUs. The duties involve support to the OIM in marine related matters including, but not limited to, maintaining watertight integrity, inspecting and maintaining mooring and towing components, and the maintenance of emergency and other marine related equipment. A barge supervisor, when assigned to a MODU is the equivalent of a conventionally licensed mate.
Boatswain: the leading seaman and immediate supervisor of unlicensed deck personnel who supervises the maintenance of deck gear.
Chief engineer: any person responsible for the mechanical propulsion of a vessel and who is the holder of a valid license as chief engineer.
Chief mate: the deck officer next in seniority to the master and upon whom the command of the vessel will fall in the event of the incapacity of the master.
Designated duty engineer: a qualified engineer, who may be the sole engineer on vessels with a periodically unattended engine room.
First assistant engineer: the engineer officer next in seniority to the chief engineer and upon whom the responsibility for the mechanical propulsion of the vessel will fall in the event of the incapacity of the chief engineer.
Master: the officer having command of a vessel.
Mate: a qualified officer in the deck department other than the master.
Offshore installation manager (OIM): a licensed officer restricted to service on MODUs. An assigned offshore installation manager is equivalent to a conventionally licensed master and is the person designated by the owner or operator to be in complete and ultimate command of the unit.
Operator: an individual licensed to operate certain uninspected vessels.
Pilot of towing vessels: a qualified officer of towing vessels operating only on inland routes.