I also had a near miss with that very rock some years back. I sailed out of Blue Hill Bay at that time and we typically would be in Camden and headed out for Eggemoggin Reach or Pulpit. Well, one fine day I actually was close enough to see the rock pass by my starboard side at close to high tide when it was covered. Never again did I ever go through that passage to Mouse after that scare. This was before chart plotters and I completely underestimated the southward set from the ebbing tide. It could well be that they set a way point north of the rock but didn't actually create a route so they had no measure of their cross track error south. Easy to do if one is unfamiliar with the waters. I'll say this though if I were skippering a $2.5 M boat with 8 people aboard I would be keeping to marked channels.