The Deck officers
Deck officers are in charge of the navigation of the ship. In addition, they are incharge of the cargo that a ship carries.
The Captain or the Master of the ship is the overall in charge. He is responsible for the safe navigation of the vessel and is incharge of the ship, all the officers and crew, the safety its crew and the cargo. He has, working under his command, the first mate, second mate and third mates, all of whom have navigational and cargo duties. The Chief Engineer and the Engine Department also report to him for all operational matters, and so do all other Departments on board.
The First Mate / Chief officer is the second in-command. He is incharge of cargo, maintenance of the Deck Department and crew discipline.
The Second Mate / Second officer, assistant to the First Mate is in-charge of navigational equipment and charts. He is the 'Navigating Officer'. He reports to the Chief Officer on cargo matters.
The Third Mate / Third officer is responsible for keeping lifeboats, liferafts and other safety and firefighting equipment in order. He reports to the Chief Officer on cargo matters and assists the Second Officer in the upkeep of nautical publications.