I can’t think of an occasion when  you would need a 100% waterproof USB mouse, anyway I am sure there is someone out there who could use one.

The USB Waterproof mouse is a 5 button silicone, optical scroll mouse which is also mildew resistant as well as waterproof, ideal if you want to use it in the shower or bath.

This waterproof mouse features an 800 dpi resolution, and it measures 130 x 80 x 48mm, if you want one they are available for $17.00 from USB Geek.