D-Day's Sunken Secrets

June 6 1944 saw the world’s biggest amphibious assault, one of the most important military campaigns in history and a pivotal moment in the Second World War. For generations, historians, archaeologists and other experts, in their attempts to reconstruct the events of the day, have scoured every battlefield – except one. Just off the coast of Normandy is a lost graveyard, where hundreds of objects lie on the sea bed.