They were sent to attack warships and heavily defended ports in collapsible, two-man canoes. Armed with limpet mines and other contact explosives, they were detailed to operate undetected in hostile waters, delivering their deadly payloads to the heart of the enemy. Speaking with survivors we get an intimate look at what it was like to participate in these death-defying missions. Military historians reveal how the programme was the brainchild of Royal Marine Major "Blondie" Hasler, who was ordered to stop the flow of German blockade runners into Nazi-controlled ports. Named after their flimsy crafts, which were dubbed "cockles", Halser's men earned their reputation with a 90-mile trip up the Gironde River to the port of Bordeaux, which they attacked with devastating effect. It was just the first of many such operations, including an astonishing 1,500-mile trip inside Japanese territory to attack the port of Singapore!