When my Catalina 320 was being commissioned in 1999, we had a tropical storm pass just offshore. The boat was in the water at that point, but mast had not been stepped. Dealer anchored the boat out in the river with two anchors
on a spread from the bow. The storm largely passed us by, but the wind blew much of the water out of the river. Next morning, I went to check on the boat. When I saw it, it was upright on the wing keel, but the rudder had sunk into the ground, so the boat was at an angle, with stern touching water at that point. A fellow sailor saw the boat about 30 minutes before I did, and at that time, he said it was sitting perfectly level on it's lines
balanced on the keel and steadied by the two anchor rodes
...i.e. like the one pictured in the post above. I was concerned that we might have damage, but we did not. Later in the day, the water came back up to near normal and the boat resumed floating peacefully at anchor
. Of course, this situation was totally unstable and the boat could have gone over at any time if the supporting soil gave way or wind/wave action hit it the right way. Some EU boats (often twin keelers) are designed to rest on their bottoms when the tides go out. Also, some swing keel boats. I wouldn't want to trust working around a typical single keel boat without some sort of secure steadying arrangement (pilings with boat tied securely to them).