If the concern is about water tightness, I suspect that the handle itself might suffice. It has a rubber O-ring for that purpose. I don't recall seeing the results of any tests to determine just how water tight the handle is...
Hopefully others can provide other insight to this.
Larry
Larry, and others,
The handles are water tight just with the O-ring from my experience. Here is a pic of one of my 18's on the bed of a mountain stream in West Virginia from when we took the kids camping a few years ago. I took numerous pics with it in the water and didn't get any water inside the handle whatsoever.

~dale