Captains make sure that machinery and equipment are in working order. They oversee the loading and unloading of passengers or cargo. Captains keep logs and records of the ship's movements and cargo. On large ships, captains have deck officers or mates as assistants. Merchant marine ships have a chief or first mate, a second mate, and a third mate.
Mates oversee the operation of the vessel and stand watch for part of the day.
On smaller vessels, there may be only one mate who alternates watches with the captain. Engineers operate, maintain, and repair the engines, boilers, generators, and other machinery on the ship. Assistant engineers oversee the operation of engines and machinery on their watch. Ship Officers and Engineers is a specialty of Water Transportation Workers. For more information, see the Water Transportation Workers occupation.