Deck department The Deck Department is an organizational unit aboard naval and merchant ships . A " Deck Officer " is an officer serving in the deck department . Merchant shipping . The chief mate is the head of the deck department . This involves administrative tasks such as scheduling work , quality control , coordinating with other departments , and conflict resolution . The Chief Mate also compiles supply , overtime , and cost control records , and requisitions or purchases stores and equipment . Depending on the number of officers carried , he may or may not be a watch officer . If the ship carries a Second Mate and two Third Mates , he will be a dayworker , with a duty day from 0800 to 1700 ship ' s time . If only one Third Mate is carried , he will stand the 4 to 8 watch in addition to handling his executive duties . The ship ' s other deck officers , generally a Second Mate and Third Mate , are also members of the Deck Department . Each watchstanding officer is responsible for the unlicensed crewmen on his watch . In a four mate ship where the Chief Mate is a dayworker , the Second Mate will stand the 4 to 8 watch , because sunrise and sunset usually fall on that watch . In the days before satellite navigation systems , the Second Mate shot morning and evening star fixes to determine the ship ' s position . The Second Mate is also responsible for maintaining the ship ' s charts and navigational publications , the ship ' s gyrocompass , and all navigational gear . He also keeps the log extract for each voyage used by company management as a short form " howgozit " sheet , covering time at sea , time under pilotage , time in port , and types and tonnages of cargoes moved . The two Third Mates are often called the Senior Third and the Junior Third . The Senior Third Mate stands the 12 to 4 watch , the Junior Third the 8 to 12 watch . While on duty , they are responsible for handling the ship and fixing its position by shooting sun lines , taking hourly fixes from the satellite navigation gear , and piloting the ship in coastal waters ; and the Senior Third will prepare the noon position slip for the use of the Captain and Chief Engineer . In a three mate ship , the Chief Mate stands the 4 to 8 watch ; the Second Mate , the 12 to 4 watch , and the Third Mate , the 8 to 12 watch . On a fully manned ship , each deck watch consists to two Able - Bodied Seamen and one Ordinary Seaman . The two ABs will alternate between two hour tricks on the wheel in good weather by day . At night , the ABs will divide their time between the helm station , standing lookout on the bow , and standing by in the crew mess or the crew lounge for any duties that may arise . The ordinary seaman will work as directed by the Chief Mate and the Bosun during the day in fair weather , and at night alternates between standing lookout on the bow and standing by in the crew mess or crew lounge for any duties that may arise , such as calling the next watch and making sure fresh coffee is brewed . The OS , with the permission of the Chief Mate and the watch officer , may take a trick on the wheel by day to develop the proficiency required to upgrade to AB . Naval usage . In the military , the deck department comprises sailors who perform a variety of functions depending on ship type and size . Examples include maintenance and upkeep of the ship , handling of the ship ' s rigging and ground tackle , coordination of underway replenishment operations , conductance of minesweeping operations , maintenance and operation of the ship ' s boats , supervision of diving and salvage operations ( including towing ) , and serving as shipboard seamanship specialists . Undesignated seamen , or those who have not selected a rating ( e . g . job or vocation ) , are normally the most junior sailors onboard and are usually sent to the Deck Department for their first assignment .