ooooo, ok, i see what you are talking about now. i just re-read your question and realized i misunderstood it. your talking about splash water getting into the vents from the wheel when the car is moving.
this one i solved rather easy. i figure when the car is moving at a decent speed, there is too much air getting pushed thru it for any water to get past the air going out. as far as the water maybe dripping down and getting into the holes after the car has stopped moving, this one is easy as well. what i did was mark where the duct on the inside touches the fender sheetmetal. what i did was drill a hole on the very bottom of it, where it semi-exposes the rubber part of the duct. this way, any water that goes in will drip down to the bottom of the duct and just drain out. this way, no water collects and stays there.