National Geographic: Nowadays, bodies of water aren't necessarily something to build around-they're something to build on. They sport not just landfills and man-made beaches but also, in a nascent global trend, massive solar power plants. Clean energy companies are turning to lakes, wetlands, ponds, and canals as building grounds for sunlight-slurping photovoltaic panels. So far, floating solar structures have been announced in, among other countries, the United Kingdom, Australia, India, and Italy. The biggest floating...