I might have looked idiotic with my Captain America helmet, frogman fins and farmer John wetsuit, but fashion was the least of my concerns as I stood on the banks of the Clark Fork River near Missoula on a recent afternoon. For some strange reason, I had allowed a friend to convince me that it would be good fun to swim the class II and III whitewater of Alberton Gorge using little more than a chunk of foam. Neither one of us talked much about contingencies or consequences before jumping in. "You freaked?" my friend finally asked, staring at the rapids. I didn't answer, but we had one important thing in our favor: Mike Johnston, owner of Montana River Guides and one of the most knowledgeable guides in the country.