buck-man,
I built a similar one out of old pallets (4'x 4'x 4') and loaded it with cedar tree saplings and branches...I read where it was advantageous to get it up off the bottom of the pond a couple of feet, as the fish have the opportunity to swim and hide beneath it. So I built 2' rail legs on it. I left the ends open horizontally before loading it up with cedars and sinking in ~12' of water. It was buoyant and floated until I could get it weighted down enough to be waterlogged. If you are at .25 full pool, now ' s the time to do it. It will be much easier to handle in shallow water.
