Water in reverse lights

Does anyone have a good way of keeping water out of the back up lights? I noticed water in there recently and have noticed it there on a lot of other Envoys as well. On one the plastic had yellowed and I would like to prevent that from happening to mine.

Sound like a manufacturers design flaw. Is the vehicle still under warranty? Get them replaced.
Otherwise sounds like you're going to have to blow the moisture out real good and seal them up with some flowable windshield sealer or clear permatex. Are the bulb socket gaskets good?
Check with the dealer first. There may be service bulletin that is not being advertised!