I have expericenced this two times. Once on a mono hull under spin. The boat was going so fast it just kept getting lower and lower in the water until it looked like we were a foot below the surface. At that point the water crashed in on us. The other time on my TheMightyHobie18 off the wind the same thing happened.

You can talk about theory all you want on this subject but what I saw happen was the water being (displaced) pushed away from the front of the boat caused the rear to sink down until the drag caught up and slowed the boat.

The boat that you mention Mary most likely didn't have the cabin closed up when they went down.

Mike