I feel horrible for the kid. It is a tough way to lose your mum. 

Okay, having spent more than just a great deal of time at Clear Creek Whitewater Park, I have personally seen some of the most insane and stupid behavior by people either swimming there or tubing there. Almost none of them have on shoes, a PFD, and a helmet.

The first clue should be in the name: WHITEWATER. That implies rapids (even if they are man-made) and the rocks that create the rapids. Rocks and the human skull do not coexist very well. A helmet likely would have saved her life. Most people who deal with whitewater, know better than to enter a river without being properly dressed and kitted out.

I have seen very good kayakers get complacent and get a good beat down in the river. Yes, it's nice, the water is nice, the people are fun... but get a clue people, do it the right way