Special Duty Officer (Merchant Marine). An officer of the Regular Navy whose permanent status is Ensign or above.
Third Mate - The junior Officer of the ship is usually the safety Officer. Third Mate is also responsible for firefighting equipment, lifeboats and emergency systems and is in charge of a (bridge or cargo) watch.
Chief Mate - Head the deck department on a merchant vessel and serve as second in command. Primary responsibilities are the vessel's cargo operations, its stability and supervising the deck crew. Second Mate - Be in charge of navigation and responsible for maintaining the charts and navigational equipment on the bridge. Duties also entail developing the voyage plans under the direction of the Ship's Master.
Master Mariner - Possesses all the qualifications to command a ship. Candidates must be proficient in the application of a barometer, chronometer and sextant to map a course across the open ocean waters.