Do you have to buy tickets in advance or can you buy them when you get to the park?

You can do either. You may find a discount online though

Daily Admission can be purchased online in advance to at the park. However, we highly recommend purchasing your tickets online so that you can avoid having to wait in lines at the park to purchase tickets.

Either. The ticket line is long at the park so I recommend purchasing them online.

Either way..

I bought the tickets for $40 on groupon but their only good for one day. When u buy them at the park you get a day free which u have about a yr to use