I'm sure window tint spends a lot of time being wet in some parts of the world, wellington for example (just joking) i think tint has the same effect no matter what side of the glass it is on, it will always mirror the lightest/brightest side. so i guess you could apply it to the outside
At night, or when the room is really dark, my tank goes mirrored, looking from the inside out. my fighter didn't like it to much, but i'm sure schooling fish would have a field day, so to speak.