Anti Broaching Water Brake

Proper seamanship requires all hatches to be closed and secured in a situation like entering an inlet with breaking waves. Small sailboats, say 35 and under, have huge openings in proportion to their volume and can easily swamp them.

 

Yes, hatches should be secured when crossing a significant bar - but how often have yachts over about 25' been sunk by water entering the hatches in a broach?

J/24s, mini tonners, quarter tonners and trailable yachts have sunk because of water getting down below through open hatches, but the OP wrote about it as if it was common and it doesn't seem to be.

 

Some years ago I was called in to help a fellow with a 38' kid's camp commuter boat that 'broached to' frequently, scaring both the skipper and the kids. The hull was a gull wing (concave) modified V (warped bottom) planing hull with a double wedge geometry. On top of that, the LCG was less than ideal and a keel (skeg) addition made made matters worse.
After reviewing the situation I had a chat with the owner and we decided to modify the steel rudder from a flat plate to a high lift to make the boat more responsive. It did not cure the problem but did make control more effective..... and a lot less screaming & swearing

 

It is a question difficult to answer, because as far as I know there is no comprehensive data on boats broaching with open hatches.