Covered a portion of my pond with a deck so I decided to install a walk-on window above that area. This way I could easily check on the fish to be sure I didn't lose one in an area I could not see them. Turned out I loved this window at night. The pond lighting would shine through the porthole and the fish under the window looked like they were swimming in air. So glad I did this. Used two plates of glass with a sheet of plexiglass sandwiched and glued between the glass for impact protection. This is one window I really enjoy cleaning.