Slasher movies have a lot of tropes, but usually there's some kind of story involved as well. The story in this movie is extremely thin.
I kept wondering what alternate universe this takes place in, where high school students (!!) are having sex in the park, doing drugs openly, bikini car wash (in 2018? More like a wet t-shirt contest anyway), and so on.
And the park manager and staff are clearly not meant to be running a lemonade stand, much less something like this. It stretches credulity beyond the breaking point.
You kind of know you're in trouble when they add a Wilhelm scream so early on into the movie... you just know they're going for the cliches, and they don't disappoint in that regard.
Ultimately it all boils down to one big set piece (no spoiler here, it's in the movie poster and trailer) of criss-crossed blades in the water slide. But, I mean, that's really it. There are the "killer POV" shots of some mysterious person doing other things, and preparing the slide, but it's kind of boring.
By the time anything really starts happening, even the average movie watcher has figured out the "whodunit" part. Oh, and the weird end-credit scene... what the heck was that? I wondered why, earlier in the movie, there was a totally off-kilter scene with a strange kid and his injured foot. I figured it was just sloppy writing and editing (which is a good guess, because the movie is full of that), but... that's the payoff? A stupid end-credit scene? It didn't even make sense.
Don't bother watching unless you're bored. I gave it 3 stars because I did watch it while I was bored, and the best thing I could say about it is, I did end up watching 'til the end just to see if I was right about who the mystery killer is. If you want to avoid wasting your time, I'm sure some review here has a spoiler you could read.