Well, I know some makers make actual open/close vents...Picture a flat piece under each vent, that you can manually slide open or closed depending on driving conditions...The best image I can give you would be similar to the sliding locks you see on peoples doors....slide left closed, slide right open...
I guess the thinking is that for the most part, you leave them close, and when you're gonna run hard you open them up...Otherwise you leave 'em open and you have to stop in the rain and close them...
Or if you really want to get creative it'd be SICK to wire something where you can open/close vents from the inside of the car. This way you can leave them open, and justy close them when it rains from the inside....
I'm just saying, looking at the below pics those vents are pretty big and I cant see anyway of redirecting all the water...besides you really dont want water ANYWHERE inside the engine bay you know??
I mean I live in miami, where it rains like 9mos out of the year...and there's hurricanes...etc etc etc....So it needs to be something like that...