Belfast Lough is a long, wide and deep expanse of water, virtually free of strong tides. The inner part of the lough comprises a series of mudflats and lagoons. The outer lough is restricted to mainly rocky shores with some small sandy bays. The outer boundary of the lough is a line joining Orlock Point and Blackhead.
The main coastal towns are Bangor on the southern shore (County Down) and Carrickfergus on the northern shore (County Antrim). Other coastal settlements include Holywood, Helen's Bay, Greenisland and Whitehead.
Popular for sailing, the lough has three marinas: one at Bangor, one at Carrickfegus and a third located at Titanic Quarter. Belfast docks at the head of a lough contain the famous shipbuilder of the RMS Titanic fame, Harland & Wolff, is no longer building ships for the foreseeable future and has shed most of its workforce and diversified into repairing and refitting large tankers and oilrigs. Coastguard offices for the lough, although referred to as Belfast Coastguard, are located in the town of Bangor by the marina.
Belfast Lough is usually selected for sea trials of new ships. The Titanic was no exception.