Tornado

Once you venture into the long tube, you'll get faster and faster until you end up in a big funnel and try to stay in this vortex as long as possible. But eventually the end inevitably comes with a big splash into the pool of water.

Hints:
Size restriction: from 1,20m
Age restriction: -no restriction-
Weight restriction: up to 110kg
Image source: Aquopolis Cartaya