I never did enough, of course, but I did kayak a number of big rivers in my younger days and even (safely) made it down about a 15-foot waterfall. Blind, dumb luck and a massive fear-induced brace -- kept me from attempting an Eskimo roll in the middle of the waterfall. I was kayaking with a bunch of folks far more experienced than me and I was the only one who made the trip with nary a tip. Lots of crashing that day!
Mark