  LNM12/76--CGD3; REPORTS A POSSIBLE UNDERWATER OBSTRUCTION IN LAT 38/58.9N, LONG 075/06.8W (NAD27), 180 DEG. TRUE AND 500 YARDS FROM BRANDYWINE SHOAL LIGHT IN APPROX. 10 FEET OF WATER.  A DANGEROUS SUBMERGED OBSTRUCTION REPORTED, ED, WAS CHARTED.  (ENTE