The RUC

From the U.S. Army Corps of Engineers, Headquarters:

The RUC
Starting in the 1960s, the United States military explored the viability of screw-propelled vehicles for navigating the rivers and marshy terrain of Southeast Asia. In 1969, Chrysler produced the prototype Riverine Utility Craft (RUC) for the U.S. Navy. 
The RUC traveled on two aluminum rotors, 39 inches in diameter and powered by twin Chrysler 440-cubic-inch automobile engines. A test program at Waterways Experiment Station - now U.S. Army Engineer Research and Development Center (ERDC) - was conducted in Louisiana using terrain similar to Southeast Asian environments.
Top speed on water was a respectable 15.7 knots, while speeds on marshy terrain reached 25 knots. However, speeds on firm soils (reaching only 3.6 knots) weren't fast enough for a tactical application. Marsh screw vehicles like the RUC were also assessed for use in applying herbicides for aquatic plant control in the late 1970s, but never employed.
Despite creative engineering, these non-wheeled vehicles failed to compete seriously with their more conventional wheeled and tracked counterparts.
Only ten RUCs were ever built, one of which still resides at ERDC in Vicksburg, Miss.