Life at sea meant short bursts of work followed by short periods of rest, these four-hour long segments of the day are called watches.
These are the divisions of the working day as well as the members of the crew that work these shifts. Because a ship needs to be manned 24 hours a day, the crew are split into two or more teams or watches so that they can sleep and relax when not keeping watch.
The first watch is from 20.00 until midnight; the middle watch is from midnight to 04.00; the morning watch is from 04.00 until 08.00; the forenoon watch is from 08.00 until noon; the afternoon watch is from noon to 16.00.
The dog watches
The next two watches are divided into 'dog watches' – the first dog watch is from 16.00 until 18.00 and the last dog watch is from 18.00 until 20.00.
The dog watches divide the 24 hour working day into an uneven number of watches so that the watch keepers do not keep the same watches everyday.
On off on off…
Because, typically, a mariner in the Royal Navy would work one four-hour watch and then rest for four hours before working the next watch, the sleeping patterns would be very different to those kept on land. Different watch systems do exist though and where there are three watches, a mariner could expect a much longer rest period between shifts.