WATCH, in the navy, the space of time wherein one division of a ship's crew remains upon deck, to perform the necessary services, whilst the rest are relieved from duty, either when the vessel is under sail or at anchor.
The length of the sea-watch is not equal in the shipping of different nations. It is always kept four hours by our British seamen, if we except the dog-watch, between four and eight in the evening, that contains two reliefs, each of which are only two hours on deck. The intent of this is to change the period of the night-watch every 24 hours; so that the party watching from eight till 12 in one night, shall watch from midnight till four in the morning on the succeeding one. In France the duration of the watch is extremely different, being in some places six hours, and in others seven or eight; and in Turkey and Barbary it is usually five or six hours.
A ship's company is usually classed into two parties; one of which is called the starboard and the other the larboard watch. It is, however, occasionally separated into three divisions, as in a road or in particular voyages.
In a ship of war the watch is generally commanded by a lieutenant, and in merchant ships by one of the mates; so that if there are four mates in the latter, there are two in each watch; the first and third being in the larboard, and the second and fourth in the starboard watch: but in the navy, the officers who command the watch usually divide themselves into three parties, in order to lighten their duty.