yeah youre right, paddling claims a really surprising number of lives. without looking into it at all, my first guess at the cause of that might be the ol' problem with water sports, where bumping your head can leave you unconscious and drowning rather than lying on the ground for a while
BASE jumping and rock climbing have to be up there on the list, no surprises there...
mtn biking is super super gnarly but i can't imagine they have nearly as many deaths as we do
i think skiing might be a little unique in that we have two major aspects of danger: the inherent danger of flying down and off mountains in new and creatively stupid ways, and avalanches. i can't think of any other sport that suffers equally from "acts of God" and our own contrived danger (and, of course, many avy incidents combine those two categories)