It isn't fully waterproof, but it could be made to be, mine has a small leak in the lens housing which could be fixed with a small bead of silicone. That and some teflon tape for the threads and it would be perfect for small dunks I think.
Step 1: Components
1. Old plastic Flashlight that has same diameter as camera lens.
2. (Optional) Scrap plexiglass
3. Tough Ziplock Bag.
Step 2: Lens Assembly
I still did get a bit of tunnel vision on the left side, due to my clumsiness.
Step 3: Baggy Baggy
Before you insert the assembly into the hole, put a small bead of silicone around the flange outer edge, so the bag will be glued and sealed to the lens assembly. (I forgot to do this but intend on going back and doing it).
Step 4: Conclusion!
Voila! It is done, mine works pretty well in the rain despite it being a 1 hour project. The ziplock bag I used was somewhat heavy duty, it housed an electronics project that I did while in college.
Step 5: Sample Images
The first picture is with Nightmode On, the second is with Nightmode Off, the Last image is one I took before I put the lens assembly into the bag and before I scuffed up the plexiglass lens, there is more tunnel vision in this then the final product because I hadn't filed away enough at the time.