The 500 pound World War Two device was picked up during dredging work.
West Dorset MP Bins Government Documents
Cabinet Office Minister and Wesy Dorset MP, Oliver Letwin, has apparently been dumping government documents in park waste paper bins.
The Daily Mirror reported that Mr Letwin had been seen disposing of papers at a park close to Downing Street on five separate occasions.
The newspaper said the MP discarded more than 100 papers, including correspondence on terrorism and national security as well as constituents' private details.
One document was said to describe how intelligence chiefs ''failed to get the truth'' on Britain's involvement in controversial terrorist interrogations.
The West Dorset MP reportedly tore up the documents but did not shred them, leaving them still legible.
Pictures published in the newspaper show the MP apparently about to drop papers into a bin while talking on a mobile phone, and in one image he appears to hand papers to a cleaner holding a bag.
The papers are said to date from July 27 2010 to September 30 2011, and include five Intelligence and Security Committee (ISC) letters.
In one, MP Andrew Tyrie reportedly tells ISC chairman Sir Malcolm Rifkind the committee ''failed to get to the truth on UK involvement in rendition''.
Another discarded document refers to al Qaida links to Pakistan, the newspaper claimed.
Prime Minister David Cameron, Liberal Democrat leader Nick Clegg and Chancellor George Osborne are all said to be mentioned in the dumped papers, as are organisations including the Ministry of Defence, the Home Office and the NHS.
The Mirror described Mr Letwin's actions as a ''security breach'' , but a spokesman for the minister insisted that the papers did not contain any sensitive material.
''Oliver Letwin does some of his parliamentary and constituency correspondence in the park before going to work and sometimes disposes of copies of letters there. They are not documents of a sensitive nature,'' the spokesman said.
640 men were killed when the South African troop carrier was hit by a cargo ship in 1917.
The 79-year-old man suffered a serious head injury in the Cranmer Road car park in Winton.
Two Girls Indecently Assaulted Last Sunday
Recently Played Tracks
On Radio: Rich and Zoe
6am - 10am
Text 'SOUTH' to 82122
Now playing: Non-stop hit music
Deposit £10 to get a £40 Welcome Bonus - That's £50 to play bingo, slots and more!*
Over 50 tracks to make you feel-good. New album out now...
Find your local four day weather report here.
What's happening on the roads where you are?
Make Heart the soundtrack to your day and you could be a winner with great prizes up for grabs throughout the day.
Find out more about some of the companies advertising on Heart.
Get some great ideas on how to advertise your business on radio, online and on mobile.