Pronounced "bosun" (/ˈbəʊsn/), and often spelled that way, the boatswain works in a ship's deck department as the foreman of the unlicensed deck crew. Sometimes, the boatswain is also a third or fourth mate. A boatswain must be highly skilled in all matters of marlinespike seamanship required for working on deck of a seagoing vessel. The boatswain is distinguished from other able seamen by the supervisory roles: planning, scheduling, and assigning work.
As deck crew foreman, the boatswain plans the day's work and assigns tasks to the deck crew. As work is completed, the boatswain checks on completed work for compliance with approved operating procedures.
Outside the supervisory role, the boatswain regularly inspects the vessel and performs a variety of routine, skilled, and semi-skilled duties to maintain all areas of the ship not maintained by the engineering department. These duties can include cleaning, painting, and maintaining the vessel's hull, superstructure and deck equipment as well as executing a formal preventive maintenance program.
A boatswain's skills may include cargo rigging, winch operations, deck maintenance, working aloft, and other duties required during deck operations. The boatswain is well versed in the care and handling of lines, and has knowledge of knots, hitches, bends, whipping, and splices as needed to perform tasks such as mooring a vessel. The boatswain typically operates the ship's windlasses when letting go and heaving up anchors. Moreover, a boatswain may be called upon to lead fire-fighting efforts or other emergency procedures encountered on board. Effective boatswains are able to integrate their seafarer skills into supervising and communicating with members of deck crew with often diverse backgrounds.
Originally, on board sailing ships, the boatswain was in charge of a ship's anchors, cordage, colours, deck crew and longboats. The boatswain would also be in charge of the rigging while the ship was in dock. The boatswain's technical tasks have been modernized with the advent of steam engines and subsequent mechanization.
A boatswain also is responsible for doing routine pipes using what is called a "Boatswain's Call". A common slang name for this tool is a pippity dippity. There are specific sounds which can be made with the pipe to indicate various events, such as emergency situations or notifications of meal time.
If something should happen to the Quartermaster, the Boatswain is normally the next in line.