Check engine light on. Son drove through a puddle. Any ideas?

What is your question?

My son drove through a puddle as it has been raining all day here. He said it started "running rough" afterwards and after he shut it off, came in, changed clothes and went back outside to leave to go to work 10 minutes later, the check engine light is now on and he said it feels like it's having a tough time accelerating and running rough - like it's jumping. He said he didn't go through the puddle very fast and since I wasn't with him, I have no idea but he is a teenager so his idea of "not fast" and mine are two very different things. I don't know if this make/model has a distributor or not. Could it possibly have gotten wet? Will it dry out on it's own? It has about 80,000 miles on it. Just had new plugs/battery, etc. changed about 4 months ago. It is "jumping" as he calls it whether he is driving or idling at a stoplight. Any ideas?

What makes this problem better or worse?

Just started. Drove through a puddle. Check engine light is now on.

How long has your 2000 Mercury Grand Marquis had this problem?

Just now