[1] They are typically assigned for ships in port or land naval installations though they may also be found underway on larger warships.
[3] While many watchkeepers stand watch for a few hours continuously at a time, CDOs may be on duty for longer periods, such as a day or a week.
In port and at sea, the officer of the watch is responsible to the captain for keeping the ship, its crew, and its cargo safe.
This is required for a number of reasons, such as to use charts and nautical publications, understand weather and safety messages, communication with other ships and coast stations, and to be able to work with a multi-lingual crew.
At sea, the mate on watch has three fundamental duties: to navigate the ship, to safely avoid traffic, and to respond to emergencies.