The airplane was presumed destroyed during a collision with water at 1644 Eastern time while on approach to the Nantucket Memorial Airport (ACK). The Commercial pilot was not located, and presumed to be fatally injured. Instrument conditions prevailed for the flight that departed Teterboro Airport (TEB), Teterboro, New Jersey, about 1530. Earlier in the day, the pilot flew his son to TEB, dropped him off, and refueled the airplane to capacity. Radar contact and radio communication were lost when the airplane was approximately one mile from the airport, at about 200 feet msl. The weather at ACK at 1653, included wind from 020 degrees at 17 knots; visibility 2 miles in light rain and mist; overcast ceiling at 400 feet.