A vessel's crew is separated into three main departments: Deck, Engine and Catering.
The Deck Department includes:
Master, Chief Mate, Second Mate, Third Mate, Cadet, Bosun, Able Bodied Seamen, Ordinary Seaman.
The Engineering Department includes:
Chief Engineer, Second Engineer, Third Engineer, Electrician, Fitter, Motorman, Oiler, Wiper.
The Catering Department includes:
Cook Steward, Steward.
Although crew size can very between ships, most commonly a crew is made of 22-25 persons.
To find more detail about individual roles please visit: Careers Guide