If you are staying in Astoria you have free access during your stay in the water park. If you want to use the park for a day around 300 for adult and 200+ for kids.
They had introductiry rates (for June-October 2016) "soft opening" ranging 600-700 pesos, higher rate for weekends. Senior discount honored, and bring student ID for 10% discount. No food&drinks allowed but they gave light snack and 1 bottles water. At that time park wasn't fully complete so rates may be higher now. Their Manila Sales office # is 63(02)6871111.
During my stay there (june 2016) it ranges from 600 - 700 but try to visit their website you will be able to see it their... You can also email them which you can get from their website about the promos their offer they will respond to you immediately during weekdays I tried it and its very convenient.
Get an answer from Astoria Palawan staff and past guests.