Imagine being stuck upside down, underwater, in a kayak on a raging Montana river. For author David Quammen (KWAH-men), it's the perfect time to begin thinking about the fluid dynamics. After all, he's only doing his job. Mr. Quammen is a veteran writer who has traveled from Montana to New York, from Chile to Tasmania in search of his stories. He writes frequently for Outside Magazine, and his latest book is a collection of essays, titled "Wild Thoughts from Wild Places."