I assure you the only reason for keeping the balcony doors closed is for the A/C-Heat systems. There is no way those balcony doors and windows can help keep the ship from sinking. I know that the water pressures imposed on those panels would be so great there is little one could do to prevent the water from having its way. I do not think there is much in the way of water-tight integrity engineered into these ships. At least not what I have seen in U.S. Navy ships anyway.
Enjoy the fresh air is what I say.