Studdering 2010 ford focus

I mistakenly drove through a lot of water the other
night. I hit the collection, pretty hard, because it
was dark and i couldn't see the "ocean" that was in
front of me.
Car behaved rest of that trip, but the next day, bam!
Problems.

It's now studdering and dimming a little at stops.
But once i get moving, it's fine. But once i get about
4 miles down the road, check engine light comes
on. At first, it was blinking. Now it just stays lit.


HELP! WHAT HAVE I DONE??