They can be fun in the morning, like an old video game. Later in the day, into the sun as Larry pointed out, they can be tiring. We've called a diver twice in our visits to Maine and sliced a few lines in our time. Our Sabre has an offset prop which grabs lines even under sail. But those can be reached from a dinghy and popped off. Full-keel props in apertures can motor right over, until they don't.
Be nice if, as Chris pointed out, like in Canada, they weren't there in the summer. But they're the price we pay for those beautiful cruising grounds. And great lobster!
Here, Nan guides us across the top of Allen Island in 2005: