An OS is generally not required to stand watch, but must pass examinations on watchstanding skills such as performing lookout duty and being a helmsman. Thus an OS will often be found on a ship's bridge after working hours taking a turn at the ship's wheel or being familiarized with bridge equipment.
During the apprenticeship, an OS performs a variety of duties concerned with the operation and upkeep of deck department areas and equipment. These duties vary with the type of ship, the type of voyage, the number of crewmembers, the weather, the supervisor, and any number of other variables. However, in most cases, one can expect an ordinary seaman to clean, to perform maintenance, to work with deck equipment, and to undergo on-the-job-training under the supervision of senior deck department members.
|Typical ordinary seaman duties|
|Scale, buff, and paint decks and superstructure. A ship's metal structure is under constant attack from the corrosive properties of seawater. Members of a ship's deck department spend a good deal of time identifying and removing rust accumulations, and refinishing affected areas with sealants, primers, and paints to slow the oxidation process.|
|Sweep and wash deck.Excess water and salt on deck can lead to slipping hazards as well as accelerated rusting of the deck and equipment affixed to it. Ordinary seamen often bear the brunt of the swabbing duties, and many look forward to earning their able seaman's ticket and being done with swabbing.|
|Splice wire and rope.A proficiency at splicing, knotting, and marlinspike seamanship have identified able seamen for centuries. In the modern merchant fleets, a proficiency for this sort of work is a requirement for certification as an able seaman. Thus, during the period of apprenticeship, it is customary for the crew to challenge an ordinary seaman, and call upon the OS to demonstrate these marlinspike seamanship skills at regular intervals, under the guidance of senior members of the deck department.|
|Break out, rig, overhaul, and stow cargo-handling gear, stationary rigging, and running gear. Depending on the type of ship, it may undergo routine cargo onloads and offloads. On container ships and roll-on roll-off ships, this requires the staging of large amounts of equipment, such as twist-locks, braces, ratchet-straps, tie-down rods, and so forth. These are generally kept in storage during a voyage, so that they won't get thrown by the ship's movement. Thus, the ordinary seaman is often called upon to move this sort of equipment from storage areas to cargo areas.|
|Secure cargo. Cargo must be secured, or fastened to the ship, when it is brought on board. Depending on the type of ship and the type of cargo, this process may be nearly automatic or a very customized operation. During a voyage, cargo is regularly checked to look for wear and tear, broken or compromised securements, shifting, or any other sort of noncompliance. If irregularities are found, the deck crew must respond by resecuring the cargo. Finally, near the end of the voyage, securements may be exercised or loosened to avoid problems with discharge.|
|Launch and recover boats. One of the proficiencies that must be demonstrated to pass the examination for able seaman is a proficiency in all aspects of work with lifeboats. International regulations require merchant ships to run regular lifeboat drills, and the ordinary seaman is customarily given a variety of duties during these drills to become familiar and comfortable with launching, commanding, and retrieving a lifeboat.|
On specialized vessels, an OS may have unique duties. For example, on research vessels, an OS may rig and operate hydrographic and other specialty winches; handle and stow oceanographic explosives; and stage and stow beach support equipment.
Time served in certain training programs and school ships may be substituted for the time of service listed above. Special certificates of service are available for Able Seaman, Great Lakes—18 months service, Able Seaman, Any waters—12 months, Able Seaman, Tugs and towboats—any waters, Able Seaman, Bays and sounds—12 months, vessels 500 gross tons or less not carrying passengers, and Able Seaman, Seagoing barges—12 months.