Schliterbahn (German for slippery road) is a 'branch' of the water park by the same name in San Marcos, North of San Antonio. This version is not nearly as big, but it will do if you're into this sort of thing and want to slide down the tubes instead of swim in the Gulf.
There is also a restaurant serving seafood (The Shrimp Haus) which doesn't require the paying an admission fee.
It's a great water park to visit with your family, friends, etc. It can be for all ages. So many things to do there! Great water activities, great souveniers, great food.