Obviously, it's needed to do things like steer and propel...

Obviously, it's needed to do things like steer and propel and make (the kayak) go, but it's real critical should he flip over, upside-down. He needs two arms to be able to get back upright so he doesn't drown. That was one of the neat things that he was able to master, and really has less to do about the arm and more to do about him.