97 Accord LX, 4dr sedan

I have a similar problem too. Water accumulates on the floor in front
of the right hand side back seat. It seems to only happen because of
rain. It seems to me that driving through puddles is enough to get
water inside. And keeping my car still (not driven) under rain is also
enough. I've never seen water on the walls or doors. I've tried to run
water on the car with a hose, but I haven't noticed water coming in.
Perhaps, it gets in from the bottom.