http://www.nationmaster.com/encyclopedia/DUKW
http://en.wikipedia.org/wiki/DUKW
In my T2k game the largest number of them in use are with the 1st brigade 49th Armored. They acquired about 90 of them (plus signifigant spare parts) while passing through the Wisconsin dells in early 98. My morrow project also uses them around the great lakes and some major rivers.
Edit Paul according to Wikipedia the Russian BAV 485 is also close.