I read that more as a snide remark from the author. Floating down a raft on the Mississippi, specifically this, is what Huckleberry Finn cemented in the collective consciousness. Why not a kayak? Why not not another river? The brand (raft, mississippi) is so strong that people who have not read the book, are saturated with the idea nonetheless. 99% have not read the book, but most of us can so easily conjure up the image.