Mitsubishi Repair: Water in the sill ?, drip pan, road debris

Question
Hi, recently it has rained for 3 days. Now when I brake or accelerate I can hear water moving back and forth in the passenger side sill it sounds like there is quite alot of water inside. Where would be the most likely place the water is getting in? I suspect that it would be around the windscreen due to the amount of water I can hear , but it only seems like it is on the one side of the car. Thanks in advance for any help.

Answer
Mark,
Water may be seeping in through the fresh air duct, located just under the windshield outside the the car.  This may even be caused by a clogged drain hose in the A/C drip pan.  When the A/C runs, it creates condensation in the heater box.  As this water accumulates, it eventually drips out of the car via a drainage hose.  This hose can get clogged by road debris or even insects.  Many times the A/C will come on any time you select the windshield defroster.  Have your mechanic check those areas for the problem.
Good luck!