At 14:10 EDT, a Cessna 172S sank in Lake Michigan two miles west/southwest of Muskegon. The pilot and passenger received minor injuries from hypothermia. The pilot said ATIS reported a ceiling of 1,400 feet prior to his departure, and he received a special VFR clearance to depart. He flew out over Lake Michigan and the visibility dropped to zero in fog. He requested vectors back to VFR conditions and was trying to return to the airport when the airplane struck the water. The pilot was not instrument rated.