The breakwater is around 1,700 yards (1,600 m) long, stands in around 11 metres / 36 feet of water and was built by John Rennie and Joseph Whidbey starting in 1812.

In World War I this natural barrier was supplemented by other obstructions to prevent submarines and small ships attacking the naval base.

In addition to ships of the Royal Navy, large commercial vessels, including ferries to France and Spain use the Sound from Millbay Docks.

[1][2] Mount Batten, a former Royal Air Force flying boat and search and rescue base, is located at the northeast corner of the Sound.

The Titanic was due to have docked here briefly on its return voyage to Britain, and the ship had a painting of Plymouth Sound on board.