Sound, or locally just The Sound, is a bay at Plymouth in England
.Its southwest and southeast corners are Penlee Point in Cornwall
and Wembury Point on Devon
, a distance of about 3 nautical miles (6 km). Its northern limit is Plymouth Hoe giving a north-south distance of nearly 3 nautical miles (6 km).
The Sound has three water entrances. The marine entrance is from the English Channel to the south, with a deep-water channel to the west of the Plymouth Breakwater. There are two freshwater inlets: one, from the northwest, is from The River
Tamar via the Hamoaze and Devonport Dockyard, the largest naval dockyard in western Europe
. The other, at northeast, is from the River Plym disgorging into its narrow estuary, Cattewater harbour between Mount Batten and the Royal Citadel.
In addition to ships of the Royal Navy, large commercial vessels, including ferries to France
use the Sound from Millbay Docks. Fishing vessels use it from Sutton
Harbour beside the old town of Plymouth, called the Barbican. There are marinas at Sutton Harbour, Mount Wise in the Hamoaze and at Turnchapel.
Over the years, the Sound has been defended by Drake's Island, Picklecombe Fort, Cawsand Fort, the Breakwater Fort, Fort Bovisand, Staddon Fort and Stamford Fort.A harbour and reservoir were built at Bovisand before the fort existed to supply men-o-war anchored in the Sound with fresh water. Joseph
Whidbey supervised the building of the Breakwater from Bovisand Lodge, from which there is a view down the full length of the breakwater.