A bomb that has lain on the floor of Loch Striven in Argyll for more than 70 years has been refloated.

It was left on the loch's bed following an innovative wartime experiment to "bounce" 6600lb of explosives across water into enemy targets.

Known as Highballs, one of the estimated 200 historic bombs has now resurfaced after an audacious mission by a team of British Sub-Aqua Club (BSAC) scuba divers.

It comes in time to mark the 75th anniversary of the bouncing bomb Dam Busters raid during the Second World War.

The huge ball was "hooked up" and brought to the surface by the scuba diving team and deposited into a box to be taken off shore by the Royal Navy.

It is hoped another of the bombs will be refloated by the divers in the coming days.

The navy will next use a crane to lift the two bombs directly into 1m x 1m wet transportation tanks to stop them from deteriorating, similar to how the Mary Rose ship was raised in 1982, 437 years after Henry VIII's flagship sank.

It is expected the navy will next transport the Highballs on Sunday to an appropriate concrete quayside, possibly Largs or the Royal Navy base at Faslane.

From there, one will be taken directly to the DeHavilland museum in Hertfordshire and one will be taken back to East Cheshire Sub-Aqua Club's base in Macclesfield, Cheshire, where it will be looked after until September or October.

It will then be delivered to the Brooklands Museum in Surrey to complete the Barnes Wallis collection.

The project is being backed by Mary Stopes-Roe, the daughter of late British engineer Sir Barnes Wallis, who invented bouncing bombs.

Appalled by the rising numbers of casualties during the Second World War, Sir Barnes set his engineering mind to work on trying to shorten the war and reduce loss of life.

The result was his bouncing bomb, designed to take down enemy targets.

They were made to fall while spinning, like stones skimming water, with the resulting splash an explosion capable of bringing down heavily fortified German dams.

The idea was startling for its time and considered outlandish, with his own boss at wartime manufacturer Vickers-Armstrongs forbidding him from working on the "absurd" project.

That all changed when Prime Minister Winston Churchill heard of the plans and sanctioned funding for testing.

Sir Barnes produced various prototype bouncing bombs - the dams bomb or Upkeep; the anti-ship bomb the Highball; the Grand Slam, which was a 22,000lb earthquake bomb; the Tallboy, which was a 12,000lb earthquake bomb, and a 4000lb earthquake bomb purely for aerodynamic testing.

More than 200 of the Highball bombs were tested at Loch Striven. They were intended to be used on enemy ships but never became operational, and 198 of them still lie scattered on the floor of the loch.

There are currently no Highballs on display to the public and the aim is to place the two bombs in British museums in time for the 75th anniversary of the Dam Buster raid in 2018.

The Highballs were the naval or anti-ship version of the cylindrical shaped Upkeep bouncing bombs used by the Royal Air Force in the ambitious raid in 1943.

On the night of May 16, 1943, a total of 19 Lancaster bombers belonging to the RAF's 617 Squadron took off from Scampton in Lincolnshire with Upkeep.

Called Operation Chastise, they had three primary targets deep in Germany's industrial heartland of the Ruhr: the Mohne, Eder and Sorpe dams.

The Mohne and the Eder were both successfully breached, while the Sorpe was damaged but not destroyed.

Of the 19 crews from 617 Squadron that set out on the raid, only 11 returned, with 53 men killed and three captured and taken to POW camps for the rest of the war.

Sir Barnes later wrote that: "For me the subsequent success [of the raid] was almost completely blotted out by the sense of loss of those wonderful young lives."