For all intents and purposes, a heavy barge whose freeboard is quite close to the surface of the water - heavy so that it does not tip up as the plane moves to the edge,
You could get a large piece of balsa cut to a length of a barge, two wide depending upon the width of the balsa, then glue pieces at 90° along the length to give rigidity, then a sheet of steel or lead slightly smaller so it is set in from the edge to act as the ballast, lay a strip of balsa along the edge of the ballast to enclose it and then cover the whole ballast and edging balsa with another set of longitudinal lengths of balsa.
IE create a sandwich like plywood of balsa, turn the whole lot over and the thick balsa side would be the top, with the ballast at the bottom, chamfer the bottom edge at 30° or 45° and paint the bottom RED and the top black varnish to high heaven after adding some towing bollards and hey presto you have a tug barge that a light plane can just drop off the back end of. lol
, I could be wrong and those in the know will correct us
