A water slide is sort of like a coaster, isn't it? In that it ... umm, okay, it's not a coaster.
But this thing is weird, wacky, strange, and above all
terrifying. Credit to
@kimahri for finding the video.
What is this, you say? It's a water slide with a twist... an
underwater slide, that used to be in the waterpark at Duinrell. The pipe is full of water. It apparently uses the "
Communicating vessels" principle to stay full of water at all times. There is a height difference between the two pools, and there must be some flow through the pipe, although not a very fast one given the pipe's diameter and the amount of water required. It could apparently be emptied in seconds in case of an emergency, which happened quite often. No wonder the slide isn't there anymore.