Hi guys - I was doing some work on my 2005 R53 S yesterday and had the rear bumper off and noticed two air ducts that open up into the inside of the cabin. You can see the two black ducts above the rear crash bar in this pic I found.

Any idea what these are for and any idea if water could get in through these. It seems like water would be able to seep in easily

 

Cabin airflow...
In the front, out the back...
I would leave them alone...car was built that way, why reinvent it if you have no issues...

 

The biggest reason for them is to be able to close the doors. Without them the air pressure wouldn't have anywhere to go and it would be really hard to close the doors. Or worse pop up the sunroof.

 

I have been having trouble with water getting into the rear of the car and slowly building up where the battery is. I think it might be bc my third brake light is completly smashed in so I am replacing that but I also took off the bumper to take a look around and those air ducts were the only thing I could think of.