I would think a boat that is caught within the perimeter of one of those bubbles would sink due to the change in density.
My late uncle was a British Master Mariner & Admiralty lawyer working for Lloyd’s Of London. I remember him talking about a weird claim that they contested of a ship being swallowed up by what was assumed to be a whirlpool (at sea? Hmmm....) off of the Aleutian Islands. Ya don’t suppose...
Can you imagine the water displacement rushing back to fill that void as well? A ship would drop right down through it, then the walls would slam shut. Horrible way to live your last few seconds on earth...