An even more interesting idea of spreading weight was the "swimming" tanks invented by top military GENIUS AND HERO (!) General Sir Percy Hobart ("Hobo's Funnies"). See Wikipedia. A steel frame around the top of the turret and bodywork was enclosed and sealed in rubberised canvas, the tank settled into the water until the weight was displaced, and they worked brilliantly.
Americans (sorry Jim et al !) say that they were a complete disaster on D Day, where 79 of the 80 US ones sank. However the instructions were very clear that they must be launched from less than 3 miles off-shore, at defined water depth, wind and tide speeds, and were forbidden from going diagonally across the current; all those used in accordance with the instructions landed safely. I have seen film of them, and the tanks are almost totally submerged. If/when swamped, they take about 20 secs to evacuate, but 3 secs to sink! Any volunteers?
I have friends in a Hants/Dorset Morris side called The Hobos, in honour of the great Sir Percy. One of his few unsuccessful inventions was the Great Panjandrum, immortalised on Dad's Army....a giant rocket-powered double catherine wheel packed with explosives.
