More than 80 years on from the Dunkirk and Operation Dynamo, in which hundreds of thousands of British and French soldiers were saved, researchers are identifying the ships that sunk as they helped in the heroic effort. With an array of technology, archaeologists on board the Andre Malraux are able to scan the wrecks, cataloging an unseen underwater heritage. "It's quite an emotive feeling" says Mark James, a geophysicist from Historic England, "you realise the human sacrifice that was made".