There are a few 13's as you can see. There is another one in the reefs . The firing range area is surrounded by a string of bouys that are numbered also. The chart I have for that lists them all and where they are. #13 is on the very southwest edge of Niagara reef. These are 3-4ft tall white and orange marker bouys.These are numbered 1 thru 60 with 1 starting near L can going east to Niagara then following a line to F can and back towards camp perry. The picket fence is numbered 22 thru 60. This is from a 10 yr old chart.