I wonder if vent windows would be pressure-locked or -assisted, once unlatched?

Under the not-gonna-have-the-presence-of-mind-to-do-this category, flipping the HVAC over to vent instead of recirculate should help, or better yet, unlatching the sunroof before the top goes under.

Most vehicles will float for just a bit before nosing under, so these options might just allow an exit...

Randii