Reminds me...
Saw a car the other night with taillights that were half full with water. Could see the water sloshing around inside every time the car hit a bump or went around a corner.
The light bulbs worked fine. Reminded me of those bubbling XMAS tree ornaments.
I had a water problem with one of the taillights on my old car, so I removed it from the car, took it to the sink, filled it up with water, noticed where water was leaking out, dried up the water and sealed the leaking seam up with silicone sealer. Then I put it in the oven on low heat for an hour or so to dry out the water inside and help the silicone cure faster.