It's called Verrückt, which is German for "insane." And trying to descend this waterslide safely would be utterly insane.
Let's do it!
The Schlitterbahn Water Park in Kansas City, Kansas is building the world's tallest waterslide. At almost 170 feet tall, it's taller than Niagara Falls (165 feet). The mad engineers who built it aren't sure how fast a person will go down it, but they think that a human corpse could exceed the 65 MPH velocity that this waterslide in Brazil can perform.
The Verrückt bottoms out, then rises to a 5 story hill before plummeting its hapless victims into a pool of water and the merciful embrace of death at the end.
It really needs a loop, like this slide in New Jersey.
-via Twisted Sifter
1) It sonds like it's a 3-person slide (so you must be on some kind of raft or something.
2) The engineers who designed it no doubt built models. They know the max speed you can attain, and that's how they've determined factors like how high the walls need to be, how much water needs to be there, how high the "hill" can be, how deep the pool at the end, etc.
They may be thrill-loving, but they're not lawsuit-loving.