Pedernales Falls State Park. This is a beautiful park only about 30 minutes away. There are hiking trails, a beautiful falls area, springs and the river itself. There are at least 3 swimming areas: Bee Creek (explained elsewhere), the main swimming area, which has (usually) gentle, rocky rapids and the youth-group area which has a sandy beach, deep, still water and a rope swing.
Take 290 West for about 30 miles and turn right onto FM 3232.
Bee Creek is a hidden gem inside Pedernales State Park. You have to hike a mile into the primitive camping area to get to it, but when you do you'll see water cascading down the hill and spilling into a series of deep holes. At the bottom is a deep lagoon with a cliff you can jump off of. It's best after a rain.
We got to jump off this wicked sick cliff/big rock. It was lots of fun! Nikki
Today was awesome! We got to jump off a cliff and I absolutely killed my legs! Sarah
I jumped off a 20 foot cliff. I also went into an underwater cave. Overall it was lots of fun. Neal
At Bee Creek we could jump off a cliff or swim around. There were two puddles before you got to the main swimming area and they were about 5 or 6 feet deep. Katie
Directions to Pedernales State Park: Take 290 West for 30 miles, then go North on FM 3232 for 7 more miles. Ask the ranger for directions to Bee Creek.