Aquaworx IWFCASTLE 5' x 10' MetrOasis Series Aqua Water Castle 100 gpm. All AquaWorx interactive water feature systems, also known throughout the industry as IWF systems, are made of highly-durable stainless steel that is powder-coated with a variety of different colors. We also add colorful fiberglass integral parts to our systems that have gel coat resistant UV, providing strong resistance to chlorinated water (preventing chalking), heavy rain, and preventing UV degradation.