The woman was pulled from the water around 2 a.m. Monday morning and taken to Weiss Memorial Hospital.
After she was rescued, police and fire began to search for a friend of hers who also went into the water.
Rough Lake Michigan waters prevented dive teams from getting into the water. They are hoping to get some dive teams in the water Tuesday to search for the missing man.
Instead, members of the Chicago Police Department Marine Unit periodically walking up and down the shoreline trying to eyeball anything in hopes of recovering the body of the man who went into the lake to rescue his female friend.
A witness who was with both victims says the female and her friends were drinking in a car when they decided to leave and jump in the lake for fun.
The female went in first and the male followed. The witness agreed to speak with ABC7 Eyewitness News, but did not want to be identified.
"When I called the cops I didn't see his body anymore," he said. "The girl was just floating on the water, but Victor, I didn't see him, he wasn't anywhere."