Before it was the coolest pool in Texas*...

...it was the Deep Eddy Bathing Beach.  More here.

The oldest pool in Texas, Deep Eddy began not as a pool but as a privately owned swimming hole along the banks of the Colorado River, as this 1920s-era postcard shows. Students and locals alike flocked to the Deep Eddy Bathing Beach not just to swim, but also to rent cabins, ride a zipline, go down a slide, and watch shows like Lorena’s Diving Horse—a steed and rider plunging dangerously off a 50-foot diving platform.

*Sorry, Balmorhea State Park.  Y'all are a very, very close second!