It was near high tide that I thumped those bouys. All were in East Penobscot Bay - eastward, to and including the MDI area. I saw the toggles but the buoys were all underwater. "WUMP!" and shudder through the boat is all you get. If the prop is exposed, you're sunk I'm afraid. I'd put the best shaft cutter on an exposed shaft and prop.
In my area, toggles are rare. Simply single buoys on set ends. Not only are they easy to see, they aren't sunk down at prop depth. The toggle system is really dumb. Don't go east of Penobscot Bay.