The term NAV. OFFICER is used to describe a range of naval officers, each with their own rank and responsibilities. Ensign (ENS) is the lowest rank, followed by Admiral (ADM), Commander (CDR), and finally Captain (CMDR). An Ensign is responsible for leading small groups of sailors and providing support to higher-ranking officers. An Admiral is the highest ranking officer in the Navy and is responsible for directing operations and managing personnel. A Commander is responsible for leading a ship or squadron and managing its crew. Finally, a Captain is responsible for commanding a large vessel and its crew.