Did this in Norway instead of rafting – hard hat, wetsuit, life jacket and a guide. It's wonderful being in the river like an otter, and I'm normally uncomfortable in water (can barely swim) and with heights. You need to be shown where the safe jump-in/slide-down/climb-out points are so that the scary ones are optional. They got progressively bigger and I bottled the last one – it was a scramble up a small cliff and an 11 metre drop!
It's also kinda similar to the coasteering I did in Pembrokeshire. The biggest I managed then was about 10 metres, but it had an easy scramble up and a clean jump-off into a deep pool. Scared me witless!
Do it, it's magical.