In many countries, a harbourmaster is an official responsible for enforcing the regulations of a particular harbour or port, in order to ensure the safety of navigation, the security of the harbour and the orderly operation of the port facilities. A harbor (or harbour) or haven is a place where ships may shelter from the weather or are stored. ... Seaport, a painting by Claude Lorrain, 1638 A port is a facility at the edge of an ocean, river, or lake for receiving ships and transferring cargo and persons to them. ...

A harbourmaster may either be a civilian or a commissioned naval officer of any rank. In the United Kingdom, when a Royal Navy officer serves in this capacity, s/he is known as the Queen's (or King's) Harbourmaster, and is entitled to fly a white-bordered Union Jack with a white central disc bearing the initials "QHM" (or "KHM" during the reign of a King) beneath a crown. The Royal Navy of the United Kingdom is the senior service of the armed services, being the oldest of its three branches. ... Flag Ratio: 1:2 The Union Flag or Union Jack is the flag most commonly associated with the United Kingdom of Great Britain and Northern Ireland and was also used throughout the former British Empire. ...

An equivalent position in the United States is the Captain of the Port, which is always held by a United States Coast Guard officer. The Captain of the Port, in American waters, is a U.S. Coast Guard officer, usually of the rank of captain, who is responsible for Coast Guard law enforcement activities in his area of responsibility. ... Coast Guard shield The United States Coast Guard (USCG) is the coast guard of the United States. ...