It's a shame these things disappear so fast. I still remember the 'Water Park' along the road to the airport, just past the RUPP. That went downhill fast, only a few years after its opening, and has now gone completely.
Same for the Water Park on Diamond Island, that not even lasted two years, I think.
And now this one.
I do remember there was some quite nice water park along Route 1 (or was it 2?), a few kilometres outside Phnom Penh. It was a bit hidden, off the main road. Probably gone as well.