You shouldn't have to worry about rust much if everything was dried out in a timely manner. As long as there isn't anything trapping water against bare metal, you should be fine. As for the wiring, electronics, etc, that's possibly a different story. The interior wiring will be the problem if there is one, the engine bay wiring should be ok if the car is that young and all of the environmental seals on the connectors are intact. The interior connectors don't have seals usually. Honestly, if it was just 3 or 4 inches inside, there is very little wiring down at that level to worry about.

Make sure you check the CV joints, tranny, etc., if you've got water intrusion there you're going to have an eventual failure.
Was it saltwater or freshwater?