Can you just purchase tickets to Hurricane Harbour at Six Flags?
You can just buy the tickets on online stores like http://www.sixflags.com/hurricaneharbortexas/tickets/index.aspx. Here, you will get all the season tickets, their prices and how you can collect them after purchasing. There is also an additional fee for parking and children with 2 and under are free.
I think you have to pay an entrance fee and go from there.