Tell me more about these plenum drains...
The SEAT Exeo, Audi A4, Audi A6 and VW Passat all feature a double bulkhead between the engine bay and the cabin. This is great for insulating the cabin from engine noise etc but also forms a cavity which can collect water. To stop water collecting there are two drains with rubber valves at the bottom of this cavity (or plenum if we're going to be all technical) which allow the rain water to run out but prevent road spray, etc from entering under the car.
Unfortunately rain water isn't the only thing that finds its way into this plenum, quite often it also fills up with leaves and other assorted debris and so the drain holes get blocked and the water begins to collect. Originally this plenum was covered with a plastic cover (there are plenty of posts on here about these covers) that was supposed to keep out leaves and stuff but these covers never really worked all that well and Audi decided that it would be better to leave the plenum uncovered to
help facilitate routine cleaning of this area.
VW have known about this issue for a long time and don't seem to be too bothered by it, their thinking seems to be that if the car is regularly serviced and properly maintained (including the removal of debris from this plenum) then everything will be OK.