Water leak not MGR

[RPWC]

My friend has a Golf which he only uses at weekends due to having a work van. the car faces downhill on his drive and he says each time it rains the front and rear passenger footwells fill with water.The car does not have a sunroof and he says the boot is dryad he has checked the door seal when its raining heavily to see if water is coming in, but can't see any ingress.anyone hazard a a guess where its coming from or point me in the right direction of where to look? This happens when the car is stationary not when moving so can't be coming up through the floor.