If the window is glass, you could frost it with a liquid frosting medium. Or you could put a decorative film on it for privacy and interest.

The issue with film is that it will not last in a shower area, too much moisture. It would work over a tub.

Here is a link to a unique product from Hy-Lite that can be used in bathroom interiors. Since you say the window spans both the tub and shower, it may be too large a window for this option.

http://www.hy-lite.com/Hy-lite-US-Block-Windows-Features-Products-Layout.cfm?featureID=52&featureCategoryID=14

Glass etching acid can give you a soft focus. Talk with your local stained glass craftsmen. When he comes out ask him how much to do an inside stain glass panel for the window. Or an applied lead cam that you can DIY brush on solored glass stain.

Is this an interior or exterior window? Also ground floor or other story?

DM Decos by Design carries an interesting product that are called "Recycled Glass Panels" and basically what they are are damaged and junked windshields that have been remanufactured and are often used in bathrooms. They add a cool modern interest but probably do not offer as much privacy as frosting might.

Thanks for the suggestions! Here's the problem. The view is lovely, and usually private,but both a pool service and gardening crew come back there and we never know when! We were hoping there might be a curtain / shade that was waterproof....

I think it's time for photo of this beautiful shower and tub window.

I agree with Dy, we could save a lot of time with a picture!