Hikes, River swimming, waterfalls or must see sites in or near San Antonio TX?

We will be traveling to San Antonio 2nd week in Aug. We already have Sea World, Alamo, Ripley's, riverwalk, Durty Nelly's , zoo, Natural Wildlife Ranch in the plans but are looking for more. Anything you think is a must see but Really wanting to find some sweet swim holes, river swimming waterfalls, hikes or other outdoor activites....Hamilton Pool with the 45' waterfall is so far the only place we found that we are wanting to try in this category but please help if you know more great places for swimming and such!! Thanks in advance!!!!!