I was on a budget so this is my feedback for people in a similar situation.
Firstly, you can’t bring in any food or drink. You could *probably* sneak in a few things without too much trouble but they check your bags and to be honest it’s understandable that they don’t allow it.
We brought tickets online from Agoba or something like that. That got us just a single daybed, but that was fine as we didn’t spend much time on it.
Food and drink was reasonably priced considering the quality of the facilities. Margarita pizzas were about $14 AUD and quite nice. Juices started from a few dollars and you could get Bintangs for about 5 bucks.
Eat before you arrive if you’re worried and then enjoy a few drinks in a lovely water park with fun rides, clean facilities and lovely staff. Absolutely worth going if you have kids under 15 I’d say.