Good camping sites?

Me and a couple of friends are looking to go camping at the end of summer and we are trying to find a good camping spot. We are looking to go old fashion sleep in a tent and crap in the woods camping with minimal creature comforts, maybe a water and power hookup at most. The camp site must be in walking distance of a body of water, river or lake, and not be crowded with other campers.

The camping site range is no further than about a four our drive from Corpus Christi. So anyone know of any good spots?