Around here, we call the green stuff duckweed. In summer and early fall, it can cover the water in marshes and ponds. Ducks swim through it, eat it...geese, too, the one below was looking up from a meal.
EOS 7D, EF 24-105mm f/4L IS USM @ 32mm, 1/200 s, f/6.3, ISO 100
EOS 7D, EF 100-400mm f/4.5-5.6L IS USM @ 380mm, 1/500 s, f/5.6, ISO 1250