Wow, i thought i would never finish my (crappy) rendering on time!
My idea is that lots of water gets spilled onto the shower windows and goes directly to the sewage without even touching you. Or even if it does, it mostly contains shampoo. Therefore, you could collect that water by placing grooves along the bottom of the windows, covered with grids, to avoid any hair or other impurities and send that water right back to the shower water duct, using a one-way (or venturi maybe?) valve.
I made hand-drawn sketches, and then rendered in Illustrator.
(Please don’t bash me too much, i have studied Physics, not ID!)
