All I have to add is that there was an indoor muni-pool near my home growing up. I spent a LOT of time in that pool, either just swimming, taking swim classes or getting my SCUBA certification, and for the various swim teams I was on in school. I also knew several people who worked in that pool, so I’ve been at the pool when the lights were being switched on.
The pool is empty and the water is like glass. If you don’t see an adult body resting on the bottom you didn’t look, and if you didn’t see an object floating in the pool you probably shouldn’t be out in public without a chaperone, and you have no business working in on or around a pool.
I wonder if there was foul play, or if this was just an amazing level of incompetence.
Very strange case.