Sea Captain large size character jug produced by Magrou in Portugal circa 1970. A sea captain is a title for the commanding officer of a military unit; the supreme leader of a navy ship, merchant ship, airplane, spacecraft, or other vessel; or the commander of a port, fire or police department, election precinct, etc. In militaries, the captain is typically at the level of an officer commanding a company or battalion of infantry, a ship, or a battery of artillery, or another distinct unit. The term also may be used as an informal or honorary title for persons in similar commanding roles. A heavy rope forms the handle of the jug.