The 500 pound World War Two device was picked up during dredging work.
Boscombe Gun Murder Latest
Detectives in Bournemouth investigating a murder in the Boscombe area of the town are issuing a further appeal for witnesses to come forward.
Officers are seeking information regarding two vehicles that were seen in the area between 2am and 3am on Wednesday 25 July 2012.
Detective Chief Inspector Pam Trevillion said:
"We are keen to hear from anyone who may have seen these vehicles or has any information about them."
The first vehicle is a small silver or grey hatchback, parked outside Whistons baby and toy shop in Sea Road in Boscombe.
The second vehicle of interest is a dark coloured hatchback seen in Roumelia Lane.
Detectives are also appealing for any friends or acquaintances of the victim, Reece James Menzies, to contact police as soon as possible.
DCI Trevillion continued:
"We urge anyone who knew Reece in any way or visited the address where Reece was staying to come forward.
"We understand that it is worrying for people to take the step to speak to police, but I would like to take the opportunity to reassure members of the public that any information will be treated confidentially."
Witnesses and anyone with information should call Dorset Police in confidence on 101 quoting incident number 25:046. Alternatively, call the free and anonymous Crimestoppers line on 0800 555 111 where mobile phone tariffs may apply.
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The 79-year-old man suffered a serious head injury in the Cranmer Road car park in Winton.
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