Story highlights SS Gairsoppa was sunk by a German U-Boat in February 1941

The ship was carrying a cargo of silver bullion, tea and pig iron

Only one of the 85 people on board survived the sinking

Wreck found 300 miles off the coast of Ireland, at a depth of 4,700 meters

A shipwreck laden with 200 tonnes of silver -- the largest haul of precious metal ever found at sea -- has been discovered in the North Atlantic.

The wreck of the SS Gairsoppa, a British steamship sunk by a German U-Boat during World War II, was found 300 miles off the coast of Ireland by underwater archaeology and salvage experts Odyssey Marine Exploration.

The U.S. company has explored the wreck which lies 4,700 meters down, on the sea bed, using a remotely operated submarine. It now hopes to bring the SS Gairsoppa's valuable cargo of silver bullion to the surface.

Odyssey's senior project manager Andrew Craig said: "We've accomplished the first phase of this project - the location and identification of the target shipwreck. Now we're hard at work planning for the recovery phase."

Craig said he was "extremely confident" the company would be able to salvage the seven million ounces of silver (200 tonnes), which was worth more than £600,000 in 1941.

The 412ft steel-hulled SS Gairsoppa was built in 1919 for the British India Steam Navigation Company, and originally served as a cargo ship on routes to and from the Far East, East Africa and Australia.

When the Second World War broke out, she was ordered into Britain's merchant navy.

In February 1941, the SS Gairsoppa was traveling from Calcutta, India, to Liverpool, Britain, with a cargo of silver, tea and pig iron when she became separated from the rest of her convoy in bad weather.

As the crew battled to bring the ship, which was running low on fuel, safely in to port at Galway in Ireland, she was struck by a torpedo from a German U-Boat.

More than 30 of the 85 sailors on board the SS Gairsoppa are believed to have made it onto lifeboats, but only one, Second Officer Richard Ayres made it safely home, landing in Cornwall after drifting at sea for two weeks.

Odyssey says it does not expect to find any human remains on the wreck.

Neil Cunningham Dobson, Odyssey's Principal Marine Archaeologist, said that -- as a former merchant mariner -- the story of the SS Gairsoppa had struck a chord with him.

"Even though records indicate that the lifeboats were launched before the ship sank, sadly most of her crew did not survive the long journey to shore," he said.

"By finding this shipwreck, and telling the story of its loss, we pay tribute to the brave merchant sailors who lost their lives."

The company won a British government contract to search for and salvage the ship. Under the terms of the agreement, it will keep 80% of the value of any silver recovered from the wreck.