The vehicle tumbled into a wetland at a forest preserve after leaving the northbound lanes at approximately 11:30 p.m. Monday.
A passing driver saw what happened and got into the ditch to help the trapped man, who was in serious condition Tuesday morning.
"I saw it flip. I ran into the water quick, and the door was closed on the left side because it was underwater in the mud. So, I ran around and opened it, and the guy was actually underwater," said Victor Voskovsky.
Police pulled the driver out and gave him CPR. Another car was involved and overturned, but no one in that vehicle was hurt.
Police say the driver of the vehicle that ended up underwater will likely face citations, in addition to a DUI charge.