DD tank

British multi-purpose tank of World War II able to travel on land using tracks and in water using a screw propeller.

Developed by a British engineer, Nicholas Straussler, in the 1930s the tank carried a canvas screen attached to its body which could be erected so as to provide the necessary buoyancy. It could then be launched into the sea some distance from shore, swim ashore, then blow away the screen with a small explosive charge, and go into action as a normal tank.

Five British, two Canadian and three US tank battalions were equipped with Sherman DD tanks in the D-Day invasion. In spite of sea conditions far worse than had been encountered in training, they were generally successful, except at Omaha beach where the US tanks were launched too far out to sea and most were swamped.