Shipboard Watch System

The means by which a ship is operated on a 24-hour basis is an important factor that must be considered carefully. Be it a large ocean-going vessel of a smaller river barge, any maritime ship that is expected or required to operate continuously throughout the day and night must have a watch schedule applied to it.
Ships and vessels that operate around the clock have crews that are divided into either two or three watches. The benefit of a three watch system is that all crew get a full eight hours of continuous off-duty time each day, but as the three watch system requires more hands, it is not always practical to apply to every ship. A two watch system means crew are going to get no more than four hours of continuous off-duty time on any day.
Both watches are structured on a time frame as follows:
Each calendar day begins at noon, and this watch is called the AFTERNOON WATCH (12p to 4p)
FIRST DOG WATCH is from 4p to 6p
LAST DOG WATCH is from 6p to 8p
FIRST WATCH is from 8p to 12a
MIDDLE WATCH is from 12a to 4a
MORNING WATCH is from 4a to 8a
FORENOON WATCH is from 8a to 12p (noon) at which time the deck officer will determine exactly when noon occurs (by noting when the sun stops rising in the sky and begins to set) and the new day begins. Watch times are announced with the ringing of the ship's bell to notify the change of watch. Crews are assigned to named watch teams (usually named for colors, but each ship might keep a unique tradition in this regard). One watch team is ON DUTY, while the other two are OFF DUTY. Next watch change, the first team goes OFF DUTY with the third team, and the second goes ON DUTY. At the next bell, the Second team goes OFF DUTY with the first team, and the third team goes ON DUTY. This cycle repeats for as long as the ship is underway. While in port, the dog watches are typically combined and it is a simple 4-hours-on-4-hours-off rotation offset by scheduled shore time for each watch team.