The Coast Guard says the 37-foot charter fishing boat started going down about midday Friday during a windy storm two miles east of Waukegan Harbor.
The rescue swimmer pulled five people from the lake into the helicopter. A Coast Guard rescue boat out of Kenosha, Wis., picked up the rescue swimmer and the other two boaters.
Coast Guard Petty Officer Michael Day says the boaters only had minutes before the vessel would've sunk with waves up to 10 feet.
Some of the boaters suffered hypothermia from the 50-degree water. Officials say they were stable and responding to treatment at hospitals.