Anony - 7/04/2008 2:22 PM 
Doublepost: I dont see an edit button.
If you wanted to build your own, here is a generic plan that might work:
Get some pvc pipe at the hardware store and two screw-type ends.
Drill out the ’light’ end, and get a circle of clear plexisglass the same radius as the pipe, then put some silicone or something on both ends of the pipe, cap the ’bottom’ and put a flashlight inside
Then add the glass, a little more silicone, and the last cap.
You cant turn it off underwater, but it would probably last a dive or two.