I've been white water rafting twice - once on the Nenana River in Alaska (class 4 rapids), and once in Wyoming.
When I was in Alaska, I was 13 and traveling with my parents. The group that ran the rafting trip offered two options: a scenic float down a section of the river that had no rapids, or going through the rapids. We had opted for the float because my mother can't swim. On the day of, the group leader surprised us by saying they wouldn't do the float because there were only 3 of us and they wanted a minimum of 4, and did we want to do the white water trip instead? My dad and I jumped at the chance, while my mom took a refund and took a walk instead. OMG that trip was so much fun.
I need to go rafting again.