DUKW

If one amphibious vehicle proves the idea works, it is this six-wheel-drive truck. Production reached 21,147 by the end of the war, and its hull was drawn by the yacht designer Roderick Stephens, which helps explain why a 2½-ton cargo truck behaved like a seaworthy boat rather than a floating box. It was slow afloat, with a top speed in the water of about 6 mph, but it could carry supplies from a ship straight across the beach to dumps inland, and the US military kept it in service until the 1960s. Restored DUKWs still give rides today, and the city duck tours grew out of them, most of their vehicles since given modern diesel engines. Anyone buying one should treat it as a boat first, with all the hull care that implies.