What is the cost at the out door water park?

It's one price for park , zoo, and water park. Cheaper if you buy your tickets on line

The water park is just one section (called The Hollow) of the whole amusement park. One ticket gets you into the whole amusement park. The Hollow is in the middle of it all; you have to walk through half of Hershey Park to get to it.

All in one pass along with Chocolate World, although the things inside of Chocolate World require more money.

The waterpark is included with your park admission. Season passes are the way to go if you plan on going more than 3 days. Plus lots of bonuses and free parking which is $15 normally.

If you buy your tickets at the door its $55. Buy them online its about $38.