Captains direct the crewmembers who steer the ship, operate the engines, and signal to other vessels. They also direct those who perform maintenance or operate towing or dredging gear. They check that proper procedures and safety practices are followed. 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.