I also had a water issue with my Scenic. Removing all the mud under the front wheel arches (behind the plastic cover which you can unclip) solved that problem. Under the car, not far from the front wheels, at the level of the doors you will see a couple of small drains which mightbe blocked.
make sure that under your bonnet, it is free from leaves as they might cause the blocage and make the water infiltrate through the ventilation system.
GA-GSXEFF
February 2009