It doesn’t sound to me like the boat actually sank. In the article it mentioned that they heard the rescue helicopter from within. Wouldn’t that imply that the pressure inside would be one atmosphere? Am I thinking about the physics of this wrong?
The pressure of any trapped gas will be equivalent to the depth of the lowest level containing air - so if the bottom of your air bubble is a meter below sea level, your pressure will be 1.1 atm.
Makes sense if the glass is perfectly vertical, air can’t escape and force is applied from the top. But if you capsize a glass by slightly turning it on its side such that most of it sinks and the air escapes by water displacement you would get some compression on the remaining air but its unclear how much.