I have this
problem, but is managable by opening the door before driving away.
I have been informed that it is the water running down the window into the door and there is some
problem within the door that does not allow the water to drain out, but collect between the outside and inside of the door frame at the footwell.
I thought it would involve removing the door interior and doing some investigating... however never got round to do it and just live with opening the passenger door after it has been raining to allow the water to drain outside lol..