This swimming spot is a great place to cool off in the summer and the hike isn't too hard. After a good rain, it's nice to go there and sit in the many waterfalls that spring up. There is a short waterfall that you can jump off and a rope swing.
It's a great place to experience the outdoor scene in Austin. On the weekends there will be many locals there and there will likely be drinking and music. After a good rain, it is a great spot to sit in the waterfalls and cool off.
Go during the week to avoid the crowds and lack of parking.