when I was a much younger, faster and less wise fellow I was a canoeing instructor in my Scout troop. But I was cocky and a bit of a showoff (self esteem, much?) I shot a wingdam on the Delaware at high water which at the time was rated a class V, I think (old system), in a 17' Grumman outfitter canoe with a single-blade. At the top of the 20' haystack on the end of the chute I managed to pirouette and then slide down the back side backwards. I was elated, excited, till later in the day when I saw a canoe just like the one I was in literally wrapped around a rock, wrapped as neatly as a Christmas present. Bhhhhhhrrrrrr. I think the most important thing to impress on new watermen is the absolutely inexorable power of moving water, and the inescapable consequence of mistakes or foolishness. a good thing to do is take the newb down less difficult water, but show them water characteristics that will be magnified on bigger water. One time I showed a guy about hydraulics on a low-water stream and a little piece of stick- he understood what I was talking about when the mini-suckhole yanked the twig underwater and held it there. I said, visualize you in your boat doing that...and he got it.