Get the water out ASAP...mine filled up during a huge rain storm and got into the car. Water collected under the passenger footwell and fried the CCM....costly. I tried to remove the battery but couldnt get it past the wipers so in the end simply pushed the rubber bung completely inwards and left it that way...water drained and problem solved, well, that problem at least! That was the last straw with my a4 and I drive an 11 year old merc now...