I rarely get off a rapids ride dry (I thinks I has a curse on water rides, like, everyone would be dry compared to me 98% of the time).
All the rapids in the UK suck, it's like all the parks decided to just build the worst rapids they could. Legoland's is alright on occasion but it's really painful in the way it just bashes into everything.
I really love Bagatelle's and Phantasialand's rapids, they are just flipping mental. River Quest is obviously superior just for the fact IT'S IN A BIG FAKE CASTLE and just the whole element of surprise at the top of the elevator (which is just awesome in itself).
I remember absolutely loving (despite the freezing cold weather) the rapids at Liseberg in Sweden. That got pretty much everyone drenched and was fun, simple but effective.
Drakker at Rainbow Magicland was good and so was Mirabilandia's rapids, both quite similar just with different themes, not sure what one I prefer out of them two.
But yeah, out of all of them I think River Quest has to be my fav, it's just brilliant.