Most of the people think that it's dangerous, but I can sure you that it's not, of course, if you're doing it with a good team.
As for me, it's the best way to know a wild nature better. My first experience was in Adigeya, river "Belaya"
One thing I noticed, every raft has a selfie-guy that is not rowing, throw him away on start he's useless.
By the way, water is very cold but you stop worrying about it in 5 minutes.