It looks like you're new here. If you want to get involved, click one of these buttons!
White water grading goes from 1 to 5/6. The river Exe in Exeter is generally grade 1. The lower Dart is grade 2. The dart loop is grade 2 with some rapids of grade 3.
https://gopaddling.info/blog/tips-and-advice/general-paddling/river-gradings-simple-guide/
And there there is Siberia, which is a whole world apart. Try this film from 1994 for grade 10:
https://www.reddit.com/r/Documentaries/comments/ikcrxo/a_glorious_way_to_die_1994_documentary_following/