It's a scorching midsummer day, and the sawgrass is still under a pale blue sky. Waist-deep in water and sinking slowly into the muck, I fend off mosquitoes as a man from South Florida's Water Management District mixes a bag of salt into a hot tub-sized bucket on the side of the road. Nine metres away in the marsh, another city official wearing waders and a bug hat stands on a narrow steel walkway, dangling the end of a long hose over a plexiglass chamber.