I went down the Youghiogeny River in western PA back in the 60s. It was a Girl Scout sponsored thing, so I doubt we did any that would be rated too high. My experience was influenced by the fact that I was about 14 at the time.
Although I'm an excellent swimmer, I found it a bit scary. I didn't realize beforehand that you had to sit up ON the balloon, not down IN the raft.

I had great fun until the girl behind me freaked out when we went over some rapids, stopped paddling, tried to climb into the bottom, hit me with her paddle & knocked me out of the raft.

After a ride
in the water that seemed like at least a couple miles but was probably only about a 1/4 to a 1/2, I climbed out - right where we were stopping for the night.
At that point, everyone else was given the opportunity to try what I'd just done - except that they were all put in a harness.
The guides were very knowledgable & overall I felt safe - except at that one point. (Although I was more afraid of losing my glasses I think. I'm blind as a bat w/o them!) I got back in the next morning & finished the trip. I still remember it as one of the best experiences of my youth.