You guys are making me feel ill! I ride at Lake Guntersville in Alabama, and I guess it's pretty clean, although I never thought of it that way! We get weed around the edges, but that's no big deal. The algae makes the water green and visibility poor, but the worst I have to dodge on the surface is the occasional dead bass. We have very clean lakes north and south of here - Timms Ford up in TN, and Smith lake further towards Birmingham. Both have clean cool water all summer.
I guess I'm spoiled and didn't even know it!