I'm another with the exact same problem; water in (DS high-beam) headlight.
At first, I assumed it was somehow travelling and getting into the bulb hole except that area remains dusty and never looks wet. You guys all seem to be saying that it's coming in the front and that it's all due to do loose/leaky/faulty rubber seals. I feel kinda stupid asking but.. what rubber seals?
Are the rubber seals you're talking about around the headlight assembly and
hidden behind the bumper or
can you clearly see yours from the outside?
Because if it's the latter, I'm getting the feeling that all mine are missing! That would explain a few things.
Should you be able to see a rubber seal in this photo?