Hidden somewhere in Magsaysay, Castillejos, Zambales. I think they charge P50 per person. They close at 6:00 PM, but it was indicated in their rules and regulations that they'll charge you extra for staying beyond that time. I guess it has to be arranged in advance.
Cris Aura offers separate pools for kids and adults. However, the slide is located at the adult pool, and using it plunges you to some 6 feet of water, so better get the life jacket ready if you can't swim but wish to enjoy the ride.