There's another issue that may yet be brought up.
A few years ago, a young girl was playing in a pool and got caught by the suction of the filter inlet on the bottom. It was really ugly. She didn't just drown -- she basically sat on the inlet, and the suction eviscerated her on the spot. As a result, regulations for new pools have been changed, and all newly-constructed pools have to have dual inlets separated by at least three (?) feet, or some other way of limiting the amount of suction at the drain inlet(s).
In my state, I'm pretty certain that public pools are supposed to have been retrofitted. But I don't live in Massachusetts. And even if the law requires it in MA, I'm sure Fall River is broke and didn't retrofit, and I'm sure the state doesn't have people traveling around to find out if all pools have been retrofitted.
From the videos, it looks like the slide was one of the enclosed tube type slides, so she almost certainly went down it sitting or semi-reclined, and hit the water rump-first in a more or less sitting position. Pool drains/inlets are usually located in the deepest part of the pool. If she went down in that position, it's possible that her rump settled on the suction inlet, and that she was basically trapped by the suction and couldn't resurface.
I worked for a pool filter manufacturer when I was in college. One summer I was in the factory, the next summer I did on-site service. Water as cloudy as what I saw in the videos would be a definite FAIL in the filter department. I'd guess the agency operating the pool never serviced the filter or backwashed it. They probably just checked the chlorine level once or twice a day and figured they had done all that needed to be done. Maybe not even that, because an adequate level of chlorine should keep the water fairly clear unless there's actual dirt (silt or mud) in it.
