[dragoon500ly]

Source material from "Omaha Beach, A Flawed Victory" and "Sherman".

The D-Day landings depended on naval gunfire and on a new device called a Duplex-Drive Tank. For Operation Overlord, this was a nine-foot high, waterproofed canvas skirt mounted onto a standard M-4A3 Sherman. THe shroud was held upright by thirty-six airfilled pillers and a set of collapsible metal struts.

The basic idea was sound. It is possible to float almost any size vehicle, no matter its weight, provide the shroud is high enough. But the higher the shroud, the more unstable and fragile the vehicle. At sea, the bulk of the DD tank hung some seven and a half feet below the surface of the water. Slightly more than a foot of the shroud protruded above the surface. The vehicle was propelled and steered by two 18-inch diameter propellers which were movable and acted as rudders. The best speed that a DD tank could maintain was about 4.5-5 knots. Each DD tank was fitted with a gyro compass for navigation, a platfrom on the rear of the turret that the TC could stand on and steer, a bilge pump with a fifteen-gallon-per-minute capacity and safety gear. The safety gear consisted of an inflatable life raft, a modified version of the submarine escape device (the Davis Lung) per man and an inflatable safety belt per man.

To launch the tanks, a modified LCT was used. Four tanks could be carried by each LCT and launched in less than eight minutes. DUring the rather limited testing phase, it was determined that a DD tank could traverse 4,000 yards of calm seas in 28 minutes. While tanks were deployed as far out as 6,000 yards, all training was conducted at 3-4,000 yards.

The tests also confirmed that the canvas shroud could be easily torn and that a hole larger than one foot could sink the tank. The DD tank could also be sunk by the wash of LCF, LCS and larger assault craft and that the concussion of nearby explosions could cause the metal frame to collapse.
Another issue was the limited exhaust venting of teh tanks engine, traversing more than 4,000 yards could lead to carbon monoxide poisoning of the crews.

These amphibious tanks were heavily counted on to support the Allied troops during the critical opening phase of the assault.

On June 6th, 1944, the DD tanks of B & C Companies of the 741st Tank Battalion were launched between 0530 and 0600 hours, some 6,000 yards off Omaha Beach. As the tanks rolled down the LCT ramps, some of them immediately sank, others managed to launch, but fell victims to the collapse of their canvas shrouds during the long run into the beach. Of the 32 DD Tanks launched off Omaha, only 5 reached the beach, three others were landed on the beach by the LCTs because of difficulties with the ramp.

One hunred and thrity-five men of B & C Companies of the 741st Tank Battalion went into action on D-Day. Remarkably, only 33 were lost, drowned at sea. Following D-Day, the bodies of 25 soldiers were recovered, by the end of June, 2 more bodies were recovered. These 27 bodies were the only ones recovered off the Normandy Coast.

In 1987, US Army Europe mounted a third search of the tank graveyard. A French SCUBA diver reported that he had seen skeletal remains in a tank off Normandy. A joint army/navy task force examined the remains of all 24 tanks, but no remains were found. The conclusion was that all possible remains had been recovered. No effort was made to recover the tanks and they remain at the bottom of the Channel, a mute testimony to courage of their crews.