Automotive → Water Leak

I have water coming in on my driver's side floorboard. Where would I go to get something like this fixed?

A mechanic or body shop. How about you start by giving us some details on the car. Is it vintage or new? Under warranty? Has it been in any accidents? Is it rusted to shit?

2005 Ford Explorer. Not under warranty, no accidents, and no rust.
I fixed the sunroof drains myself, so it's not that. I pulled up the carpet one day and when I ran water down the drain under the windshield, water came in.

It's from the AC.

Clean the evaporator drain.

Seconded. I had this issue in my Prius. Used some foaming AC drain pan spray, that you pump up the hose. It killed the bacteria and then allowed the drain to flow correctly.

Under the passenger side of the vehicle there is a drain line for the evaporator core. Check that first.

Compressed air works the best for blowing out a drain line.

AC is the problem 10 to 1.

Not on a Automotive AC system since you blow dirt or debris upwards which puts crap in the evaporator core housing space where it can just re-clog the line the next time the system drains or you can blow the line off the housing making the inside leak continue. It is best to clean the line manually or use a vacuum (adapted down to fit) to pull out the clog out. Now if you completely remove the drain line then you can clean it while off vehicle with compressed air and then reinstall it which is ok...

It wasn't the AC. The cowl drain was blocked.

Surprise. Glad you found what it was.

Are you sure? The cowl is outside the firewall and is sealed from the inside normally. Cowl drains when present usually end up in the wheel arch to drain outside on the ground.

He already stated in an earlier post " I ran water down the drain under the windshield, water came in." Unfortunately people jump to conclusions wanting to get their own solutions heard instead of actually reading all the facts.