The Winthrop Harbor Fire Department responded to a report of a possible missing person in the water at North Point Marina around 3:30 p.m. Saturday.
The victim, a man in his 70s, had been last seen around 10:30 p.m. Friday.
Dive and side-scan sonar technicians, along with rescue and law enforcement personnel from multiple departments in Wisconsin and Illinois, responded to the scene.
Officials found the victim in the water, under a dock, around 8:45 p.m.
The man's identity was not immediately released.