I have a small hole in the lens of the right (passenger side) headlight and it was full of about 3/4" of water, had sea monkeys living in it. A replacement lens is $200+ so I just let it dry out. I live in Arizona so we get very little rain. When the pond finally dried up and the sea monkeys were all petrified, I put a small piece of clear tape over the hole and have had no problems at all. That was three years ago.
Today I say a Honda Gold Wing Motorcycle with a clear plastic cover over the headlight to protect from stone chips. I’m going to find one that will fit (or cut to fit) over my Boxy Black Beauty’s headlights to prevent it from happening again.