I distinctly remember, when I was very young, shopping malls having waterslides. These were not the kinds of waterslides you see in parks, no. The slide part consisted of a helical tube in which you would slide down until you hit the surface of the water, then you would swim down through the rest of the helix into the pool. This pool was actually a truncated pyramid, completely transparent, and completely filled with water. Someone coming down the slide would swim down to the bottom and into the exit, which lead to a water filled stairway. They would then have to walk or swim up the stairs to the surface.
This didn't exist. This couldn't have existed. As I remember it, it would have been a death trap. A sealed vessel you can only enter by a helix or a stairway? People would be passing out and expiring so often they'd have to put a hinged lid on top just so they could fish out all the the corpses.
For some reason, though, I remember waiting in line with my sister while she went down it. I remember wanting to use it very much and being told I was too young. I don't know where it came from. Did I just dream the whole thing? Completely misremember a trip to a water park? Or did part of my brain get swapped with that of a version of myself from a weird science fiction world with no liability or consumer safety laws?