In general terms an able seaman, short for able-bodied seaman, is any experienced sailor capable of performing a variety of routine maritime duties.
In the Canadian Navy an Able Seaman (abbreviated AS) is an enlisted rank above Ordinary Seaman and below Leading Seaman. The insignia for an able seaman is one gold downward-facing chevron on the shoulder of the sleeves as well as the epaulets, if applicable. They are addressed as "seaman" or "able seaman."
Ordinary Seaman ← Canadian Forces Ranks and Insignia → Leading Seaman
Able Seaman (abbreviated AB) also describes a United States Coast Guard-issued qualification for merchant marine sailors. To qualify as an able seaman, an applicant must be at least eighteen years of age, meet sight, hearing, and physical condition minimums, pass written and practical examinations, and meet service requirements. Usually the written portion of the requirements are satisfied by completing a USCG-approved course that varies in length from around forty hours to over eighty.
Types of Able Seamen
Able Seaman ratings come in several flavors, each with their own restrictions and service requirements.
Unlimited
An Unlimited Rating requires three years service on vessels operating on the oceans or Great Lakes. It qualifies the holder for unlimited service on a vessel in any waters. They can make up all of the able seamen on any vessel.
Limited
A Limited rating requires eighteen months service on vessels of 100 gross tons or over that operate on the oceans, Great Lakes, or navigable waters of the United States. It qualifies the holder for limited service on a vessel in any waters.
Special
A rating of Special requires twelve months service on vessels operating on the oceans, Great Lakes, or navigable waters of the United States. This rating qualifies the holder for special service on a vessel in any waters.
Offshore Supply Vessels (OSV)
An Offshore Supply Vessel rating requires six months service on vessels operating on the oceans, Great Lakes, or navigable waters of the United States. An AB-OSV can only be employed on vessels less than 500 gross tons involved in finding or exploiting offshore mineral and energy sources.
Fishing Industry
This rating requires six months service on a vessel operating on the oceans, Great Lakes, or navigable waters of the United States, but they can only serve as an able seaman on fish processing vessels.
Sail
The able seaman-sail rating requires six months service on sailing school vessels, oceanographic vessels powered primarily by sail, or any equivalent sailing vessels operating on the oceans, Great Lakes, or navigable waters of the United States. It qualifies the holder to serve on a sailing school vessel in any waters.
Mobile Offshore Units (MOU)
Wading through the legalese, it appears a "mobile offshore unit" is another name for an offshore drilling platform.