CL 806/73 13th CGD --  A SUBM RK IN PORT MADISON BAY ABOUT 200 FT S OF THE BEACON ON THE SOUTH SHORE OF TREASURE ISLAND WAS REPORTED.  IT WAS EXAMINED BY A SKIN DIVER AND REPORTED TO BE ABOUT 10 FT LONG, 4 FT WIDE, AND 4 FT HIGH OR IRREGULAR SHAPE AND AB