Class III-IV Cossatot River, AR

The National Park Service describes it as "probably the most challenging" white-water float in the state. The U.S. Army Corps of Engineers is a little more emphatic, saying it "is the most difficult whitewater stream in the state of Arkansas."

Early Indians simply called it Cossatot—their word for "skull crusher." Today, the Cossatot River is still crushing things, but they're mostly canoes, ice chests, and the egos of over-confident paddlers.

rivers.gov/Cossatot River