2015 Ford Focus - Wet floors

In heavy rainfall my car has a fairly severe water leak into the drivers side foot-well. In very heavy rain the water penetrates as far as the rear foot-well but does not effect the passenger side. Can somebody please help me with this?
Regards. Alister. .

Check the door drains. Lower edge of the door, not uncommon to be blocked with debris. Mine would get leaves from a live oak in there. Live oak leaves get everywhere! AC drain, cabin air filter, engine air filter, everywhere!
Could be the AC drain, though on most cars the overflow would occur on the passenger side.

Do you have a sunroof? If you do, the sunroof drain is likely clogged.