It's a tried-and-true element of Dungeons & Dragons adventures: setting watches while the party is resting. In a Skull & Bones game, however, it's more than just good practice; it's the long-established custom of the sea. Using this system can help to provide a sense of realism in a campaign, and it also divides time at sea nicely into six segments for the purpose of determining encounters. (Note that the following time references use the twenty-four clock.)
Watches and Times
20:00 - 0:00 / First Watch
0:00 - 4:00 / Middle Watch
4:00 - 8:00 / Morning Watch
8:00 - 12:00 / Forenoon Watch
12:00 - 16:00 / Afternoon Watch
16:00 - 20:00 / Dog Watch
The dog watch is divided into two separate segments of two hours each, the first and last dog watches. In this way, the time periods in which different groups are on watch vary from day to day. Depending on the size of a ship's crew, there could be two groups or three. Naturally, having three watch groups means more time to rest for everyone involved.
In this way, the ship's traditional organizational scheme also provides the GM with a natural arrangment for determining random encounters. For example, there might be a 1-in-6 chance of an encounter during any watch, and so the GM rolls 1d6, with something happening for each result of a 1. Should an encounter be indicated during the dog watch, there's a 50% chance of it being during the first or last part of it, respectively. As always, the PC's should decide who is awake for each watch. Additionally, if the GM is using the system for tracking crew members as detailed in the article "A Motley Crew," specific NPC's could also be assigned to serve with the PC's.
Time is kept with a thirty-minute glass; therefore, every watch consists of eight glasses. Since the ship's bell is rung after each such half hour, time can be noted as the Nth bell during a given watch. For example, half an hour before midnight is the seventh bell of the first watch.