Had a Rare moment of sunshine today so decided to give my A4 a thorough clean and wax polish ( audi a4 2.0 TFSI turbo SE ). After 6 hours of hard labour I decided to check under the bonnet. Topped up the washer and was just checking the battery connections and noticed the well that the battery sits in was full of water , about 5 inches deep. I've never noticed this before so not sure how long it's been like this. I had to use a thin flexy tube to drain out , I then left some kitchen roll to absorb the last few millimeters. I've used a torch but can't find a drain plug , should water get in here in the first place ?. Is there a drain plug ? If so where is it ? . The bonnet was properly closed during the wash and I didn't use a pressure washer. Help please.