We utilize baffles with a polymer coated polyester filament fabric in aerated wastewater treatment lagoons all the time.
There are several manufacturer's out there, 2 of which are ThermaFab and Environetics.
Most of these are not completely watertight. The top ofthe baffle is supported on the water by floats and cabling is run beneath the floats and anchored at either end to posts on shore. The bottom of the baffles contain ballast to weight them down and also have anchors; but, they may or may not lie flat on the bottom of the basin. Particularly on the sideslopes. The baffle skirt is a one piece design.
I have seen baffles used however that are basically folded over with floats on both sides forming a U shaped cross section in the water. Sandbags are then placed in the middle of the U to weight the baffle against the floor and provide a better seal.
They can be designed with flow through windows or without.
They are easily installed by floating them across the water, installing the weights to the bottom of the skirt and then dropping the skirt. Additional anchors and cables are connected to the top of the baffle at intermediate positions to keep the baffle from waving in the wind.
A search and look at some of the manufacturer's websites might give you a better idea.
