That is wonderful stuff, & by far the easiest & one of the best looking fixes. I used the frosted vinyl on my boat 15 years ago & it is still there. The trick in applying it is to spray the window w/a heavy coat of Windex (generic ok), then you can slide around the vinyl until you get perfect placement. Then use a small squeegee (the kind you use on shower doors) to get out all the air bubbles. This also works on the vinyl “stained glass,” which I used in an old mh.
My first rehab is underway and I just noticed the full bath has a regular size window right in the center of the wall where the bathtub / shower is. So basically if you like to shower you must also like to show off to the neighbors.
Originally I was either going to just heavy duty clean the tiles (in good shape) or install a tub/shower surround…that is before I didn’t "see " the window?!?
I was thinking glass block to allow light into the bathroom.
An opening window is great for fresh air and circulation in the bathroom and to prevent mold. You could replace the window with one that pushes out from the bottom allowing air but still allowing privacy. Also use frosted glass or even artistic stained glass to prevent the neighbors from seeing inside. You will get as much or more light than glass blocks provide plus the other benefits. If the opening is quite large glass blocks might be the answer with a small window they make to place in the blocks. Shop around for the many options available for bathroom windows. Make sure that any window sill slopes down slightly toward tub so water does not puddle on the sill but instead drips back into the tub.
I have had this issue in a couple of homes. The quickest, cheapest way is to install a cutain rod and shower curtain on the inside of the tub (in front of the window). It can be pulled back to expose the window when needed but it keeps the window dry and those pesky neighbors from peeking! Be sure to cut the length so it hangs just above the lip of the tub. It’s worked for me and it’s cheap!