  H10560/94--OPR-K171-MI-94; FOUND AN UNIDENTIFIED OBSTRUCTION IN LAT. 29/44/38.64N, LONG. 093/20/34.20W (NAD83).  A DIVE INVESTIGATION WAS NOT ATTEMPTED DUE TO TRAFFIC, WEATHER, CURRENTS, AND LOW VISIBILITY.  THE LEAST DEPTH OF 4.7 METERS MLLW AND THE P