The War Office was skeptical. "Swimming tanks?" a general scoffed. "Next you'll want flying horses."
When Allied forces stormed the beaches of Normandy on June 6, 1944, they relied on a fleet of armor that seemingly defied physics. Tanks were supposed to sink. Yet, as landing craft ramps dropped miles from shore, strange silhouettes bobbed in the choppy English Channel—Sherman tanks with collapsible canvas screens, propellers churning water, moving slowly but inexorably toward Hitler’s Atlantic Wall. dd tank origin