On a family cruise in the late 60s we were sailing in company with a couple on a 38 footer, may have been a Laurent Giles design but I can't remember for sure. They followed us in to your mystery harbor, but apparently they didn't notice the detour we made to leave the red to starboard. It was dead high tide, and they went hard onto the bar. A fisherman tried to pull them off, but all he did was rip a winch off the deck. With a quickly falling tide they decided to simply let the boat lay over and wait it out, after all it was a smooth and fairly even bottom. As nightfall approached it gradually dawned on us all that the boat wasn't laying over, she was sitting upright on her flat keel perhaps 10" wide. They were still aboard and there wasn't much that could be done at that point. My parents and sisters and I took turns watching all night in case anything should happen. A breeze came up which didn't help matters, but by morning the boat was still standing upright with the tide nearly back in. They still couldn't get her off, so we eventually took her spinnaker halyard and pulled her over hard and they were able to motor off.

Years later, after her husband had died, the woman, Mary Harper, became the oldest woman to cross the Atlantic at age 79.