Rescue crews in Wilmington, southwest of Chicago, pulled a man's body from the Kankakee River late Tuesday.
A fire official told NBC Chicago the man was boating with three other people when their crafts tipped over and everyone ended up in the water.
Two people were on shore when rescue personnel arrived and a third was safe on an island.
The man's body was found in the water just before midnight.
His identity was not released by 6 a.m. Wednesday.