Headed from Gloucester to Boston with a cargo of fish oil when it foundered on November 16, 1950, the Arco No. 8 was a barge that sank off Graves Light at the approach to Boston Harbor.
The Coast Guard placed a buoy over the wreck, near the gong buoy marking Flip Rock, as a warning to mariners. The Arco No. 8 is in 45 feet of water.
What follows is information from the US Coast Guard, courtesy of FindTheData.org:
M48/50– MASSACHUSETTS-BOSTON HARBOR APPROACH-BROAD SOUND-WRECK LIGHTED BUOY ESTABLISHED; ARCO WRECK LIGHTED BUOY “WRA”, PAINTED WITH RED & BLACK HORIZONTAL BANDS SHOWING AN INTERRUPTED QUICK FLASHING RED LIGHT HAS BEEN ESTABLISHED 5360 YARDS, 304 DEGS. FROM THE GRAVES LIGHT TO MARK THE WRECK OF THE BARGE “ARCO NO. 8”. APPROXIMATE POSITION OF BUOY LAT. 42-23/24N, LONG. 70-55-10W. WRECK IS IN A SOUTHWESTRLY DIRECTION 50 YARDS, 222 DEGS. FROM BUOY.
LNM121, 122/50– (NOVEMBER 17, 1950); REPORTS SUNKEN WRECK OF BARGE ARCO NO. 8 AT BOSTON HARBOR.
CL330/51–COE T0 USC&GS DATED MAY 22, 1951; SURVEY OBTAINED LD OF 45 FEET AT MLW. BOTTOM DEPTH OF 60 FEET IN VICINITY. SEXTANT POSITION . NO SALVAGE PLANS SINCE ITS DEPTH IS CONSIDERED SUFFICIENT TO AFFORD CLEARANCE FOR TRAFFIC. COAST GUARD EXPECTED TO REMOVE MARKER BUOY IN NEAR FUTURE.
NM24/51– MASSACHUSETTS-BOSTON HARBOR APPROACHES-LIGHTED WRECK BUOY DISCONTINUED; ARCO WRECK LIGHTED BUOY “WRA” HAS BEEN DISCONTINUED (APPROX. POSITION LAT. 42-23-24N, LONG. 70-55-10W. NOTE: WRECK OF THE BARGE “ARCO NO. 8” LOCATED ABOUT 50 YARDS, 222 DEG. FROM POSITION REPORTED ABOVE. LD OF 45 FEET OVER WRECK. (UP 8/17/00, SJV) (NOTE: POSSIBLY COMPLETED BY WHITING). (UP 7/2/03, SJV)
H10994/01– OPR-A397-WH; 200% SIDE SCAN SONAR LOCATED ITEM. SWMB OBTAINED A LD OF 53 FEET IN LAT. 42-23-21.66N, LONG. 70-55-05.81W. EVALUATOR RECOMMENDS DELETING CHARTED 45-FOOT CLEARED DEPTH AND CHARTING A 53 WK AS SURVEYED. (UP 9/1/04, SJV)
24 NO 886; BARGE, 316 GT; SUNK 11/16/50, MARINE CASUALTY; CLEARED TO 45 FEET.