One of the unique features of Lake Osprey at Oscar Scherer State Park is the artesian spring that feeds it. Someone at some point put a well in near the lake, and they struck an underground spring that forces water to the surface through the pipe you see above. They've built a little pool around it to keep the flowing water from eroding the bank too heavily, and that's what you're seeing above. The water is crystal clear, and looks like you could drink it.
However, sometimes looks can be deceiving. All of the white you see on the bottom of the pool is a form of algae or bacteria that grows only in the presence of sulfur. And when you get close to this water, you can smell the sulfur (or I guess it's hydrogen sulfide you smell, but whatever). It's nasty. After trickling down a short stream (maybe 30 feet) into the lake, most of the sulfur that was dissolved in the water has escaped, and the lake itself doesn't have a smell to it. When I was little, we had a deep well out back, and the water from it would often smell of sulfur. You could drink it if you had to, but it wasn't the best stuff on earth.
I always make it a point to check out this little pool when I'm at Oscar Scherer, and this is the first time I remember seeing so much bright green algae in there. It's usually all white, making it look like someone painted it. I thought it looked pretty neat when the sun lit it up.