For WWII, General Motors built an amphibious vehicle officially named DUKW and most commonly referred to as "The Duck."
Just over twenty-one thousand Ducks were built for it's three years of service during World War II. (It was also used during the Korean War.) Powered by a 6-cylinder engine, the 6.5-ton Duck averaged 50 mph on land and 5.5 knots on water. The Duck was not armored and was equipped with a bilge pump in case the thin hull suffered large bullet holes and took on water. The tire pressure could be varied from inside the cab, to full inflation for hard surfaces and reduced inflation for soft terrain such as sandy beaches.
The Duck was used by the US Army and Marine Corps as well as by the British and Australians. They first appeared in the Pacific conflict, at Guadalcanal, then in Sicily in Operation Husky. They were at the D-Day landing in Normandy and at three other European front invasions. Their primary benefit was in transporting supplies and wounded.