London 2012: HMS Bulwark begins exercises
HMS Bulwark has been deployed off Weymouth and Portland as part of a security exercise ahead of the Olympics.
The amphibious assault ship will be used as the police command base during Olympic and Paralympic sailing events.
Assistant Chief Constable Adrian Whiting said: "Dorset Police will have access to the widest range of maritime capabilities and expertise."
Dorset is the largest Olympic and Paralympic venue outside of London.
Mr Whiting added: "Our role includes supporting the organisers and athletes by ensuring the fields of play on the water are safe and secure - an area of approximately 50 square miles.
"To do this, we will use small watercraft, including rigid hull inflatable boats and personal watercraft, as well as launches crewed by Dorset officers and marine police officers from other forces around the country."
Capt Alex Burton, of HMS Bulwark, said security at the Games would be "robust but discreet".
The operation is supported by the Royal Navy, Army and Royal Air Force.
HMS Bulwark returns to Weymouth and Portland in July for the Games.