For duckweed I made a 6' wide frame out of 4" light weight plastic drain pipe, four 90* elbows, and two end caps. Put 3/4" PVC across the front for stability then I wrapped shadecloth around the bottom and held it together with bungee cords.
When the wind pushes the duckweed into to shallow areas, we wade out and scoop it up. In the deeper areas we drag it behind a small boat. Works great!
