Fond memories of childhood visits to a local "flume" ride, essentially a long concrete-lined ditch dug in a switchback pattern down a big hillside. Painted to make it slick, and they pumped a continuous stream of water all along it. You rode it by sitting or lying on foam mats, about 3x4 feet in size.

A ton of fun, you could get going pretty fast and you definitely wanted to have your legs crossed when you hit the pool at the bottom. Never heard of anyone getting hurt though, other than some mild abrasions if you slipped off the mat -- the concrete wasn't totally smooth. The curves were pretty steeply banked and the most you could really do if you went over the side was end up in underbrush.

Terrible that adults who should know better are making rides without apparent regard for safety of the (mostly) kids that will be riding them. Those elevated trough rides do worry me, they really need to be fully enclosed anywhere there is any chance of going airborne or over the edge.