as well as 'C-1' marking it. Good distance between the buoy and the ledge with good water right inside the can. Perhaps the can wasn't in place?
The ledges in Maine are unforgiving. I've left a few pound off the bottom of my keel up there (but there's plenty more).
Interesting that the write-up says the boat filled with water when the tide came in because the companionway was open. IMHO, the boat filled with water because it had a hole in the bottom - nothing to do with the companionway.