First off, I was not me, it was a local guy who posted this on another bulletin board. I shared this to help educate others. Second this was not really "White water", just a good current through a chock point. It sounds like he went down the chute at the bottom of the photo and grabbed a limb along the side. It does not take a lot of current to flip a pontoon if you get sideways to the current. That is exactly what happen to my fishcat, I got the tube sideways against the current and I was upside down instantly. I had just come down a faster section than what flipped me.

Chattahoochee at Holcomb Bridge.jpg