The biggest attraction of San Antonio is Sea World. No San Antonio trip is complete without visiting this. Most of the times, buy the tickets at full price at the gate of Sea World. However, there are some very easy tricks to get the tickets at discounted prices, and save some money.
1) Look for tickets on craigslist
2) Try to find tickets on ebay
3) Check out some local coupons
4) Find the currently running offers

I found an interesting article that details a few simple methods to get tickets at discounted prices:
http://SaveFewBucks.Blogspot.com