Simple. It's to see the last unrun rivers on the planet. And to push the boundaries of what's considered navigable in any boat, let alone a kayak. An unrun river is the difference between buying a lift ticket and skiing a new line in the Chugach Range, in Alaska. When you repeat something that somebody else has done, the mental barrier has already been broken: You know it's doable. With a first descent, you've got to figure it all out on your own. That feeling of elation I used to get after making it through a rapid is harder to duplicate now. I've become more patient over time; I'm willing to wait for it and plan for it on a grander scale. So that when it does come, it's that much more exceptional. A first descent is a small honor, but it lasts forever.
Last January, Stookesberry, 30, paddled over Brazil's 100-foot-plus Anaconda Falls.