Considering the limitations of current waterbody restoration methods and the increasing need for techniques that can improve degraded ecosystems, this research project had the objective of using residual materials (wood ash, coconut fibers and used P.U foams) to develop and evaluate a new low-cost design of a floating waterbody treatment device, which follows the idea of constructed floating wetlands. The study consisted of evaluating the device’s performance in treating contaminated water on both a laboratory and a real scale. When installed in a reservoir, the structure considerably decreased total phosphorus concentration and increased dissolved oxygen at some points, thus improving the aquatic environment’s ability to recover itself. The study provides valuable data for future in-depth studies in which the treating structures could be further developed and applied to recover degraded water bodies at low costs.