We used to have a nasty one at the Beach water park here. It used inner tubes like that but the track was -rough, unpolished fiberglass-. My first and last time riding it a child came to a stop in front of me so I planted my foot down to try and stop my momentum. I was wearing pool shoes at the time and the razor sharp texture completely rasped the cloth part of the shoe away and a decent portion of the skin on the upper part of my foot.
I am not even sure how the fucking thing stayed open since somebody being tossed out of their tube like that would have banged against the surface of the slide and been flayed alive.