Captain is the traditional customary title given to the person in charge of a ship at sea. seacapt.com On most legal documents in the merchant shipping industry, the captain is more formally referred to as the ship’s Master. A nautical “captain” may be a civilian with a master’s license or a naval commissioned officer of any rank.
On shore, a Harbourmaster, as the equivalent chief of a port, is sometimes titled “captain” if he had merchant marine or naval rank and professional service in command at sea. Many shipping companies also hire experienced captains to run their operations department.