Thanks. Sounds possible. I guess one way to find out is to go out sailing! That's why I asked about buoyancy volume!!!!There is a little 'breathing' hole underneath the bow end of the toe-strap. Since the bow was down - I assume it filled up the hull by using this hole.
How did the water get into the hull? What should I do?
Where is this brass fitting?The gap between the deck and the bottom is sealed with a brass fitting, so check that the seal is still good. If you are certain that the mast step was not the culprit, then it could be leaking through the cockpit drain into the hull cavity if the seal there is bad. However, if the boat was tipped forward and the cockpit is full, yes, I agree with the other posters it likely leaked through the breather hole under the hiking strap.
Would baloons be the same as water bottles...
I'm not familiar with those so I can't offer an opinion. The key consideration is whether they would remain inflated bouncing around inside the hull. From your description, I wonder how sturdy they are when they don't have the ball outside them, protecting them. Kinda like the tube inside a bicycle tire or something?I was thinking more of the rubber balloons that you would find inside a ball as they are much harder to pop and are easily availible to me.