Floatovoltaics, floating photovoltaics, are being deployed at hydroelectric dams. They add to the electricity generation, of course, but they also cut down on algae and evaporation.
I can’t see people wanting to cover recreation Mecca’s like Lake Powell from shore to shore. Maybe the place to start are toxic bodies of water like Butte’s Berkeley Pit (a Superfund site legacy from mining) or coal slurry ponds to keep wildlife out, if the wiring wouldn’t dissolve in the chemical concoction.
Floating solar is more than panels on a platform—it’s hydroelectric’s symbiont - Ars Technica https://apple.news/ALXAOel1JT0G4hA7V8PDdOg