watch

watch.
1. The division of the 24 hours of the seaman's day into periods of duty of four hours. Thus there should be six four-hour watches in a day, but as this would entail ships' companies, organized into two or three watches, keeping the same watches every day, the evening watch from 1600 to 2000 is divided into two two-hour watches, known as the first and last dog watches. Starting at midnight, the names of the watches are: Middle Morning, Morning, Forenoon, Afternoon, First Dog, Last Dog, and First. Those on duty during a watch are known as watchkeepers.

See also ship's bell.
2. The basis of the internal organization of a ship's company whereby men can obtain regular periods of rest although the work of the ship must go on day and night. The crew is divided either into two watches (port and starboard) with each watch alternating their periods of duty, or into three watches (usually red, white, and blue), so that every man gets two periods of rest to every one period of duty. The periods of duty correspond to the watches into which the seaman's day is divided.

3. As a verb, a navigational buoy is said to be watching when it is floating in the correction position as indicated on a chart, and that its light, or other signal, if it has one, is in working order. Other buoys are watching when they are carrying out the purpose for which they are intended, e.g. an anchor buoy.