Pirana is a rapids ride in Alternative Realm at Efteling. While it's not a "must do," it is also recommended.
This was Europe's first ever River Rapids rides, and is still one of the best. Things start gently as your boat passes by an abandoned Mexican village...and then you find out why everyone left. Cue waterfalls, fountains, and some of the roughest rapids that you'll ever ride. The boats can also catch up on eachother because the river is very broad. "You may get wet" is a serious understatement.
Now open, or date announced:
Still waiting on these: