water on driver side. when it rains the floor is totally soaked with a puddle

check plastic flaps covering firewall from inside engine compartment.....also the tar like seals around wiring harnesses that go through the firewall. My mother's HHR had this problem on passenger side. Dealer fix $300.00. At home cost$5.50 for a tube of clear silicone.

Could be a clogged sunroof drain, a door left open, window left slightly open. Has the car been in an accident?

Very possibly that the windshield seal is bad and that is where the water is coming in from.

I had this problem, first remove the both windsheild wipers, then remove the black cowl cover, and on the passenger side you will see a black butyl patch in fromt of the fresh air intake, that path needs to be replace.