The window won't break like that under unequal pressure.Israfil said:Are you really saying you wouldn't just take a breath, break the window, and swim to safety? ^_^ Sure its easier to wait till the car fills entirely then open the door at equal pressure, but in a life or death situation methinks the old standby of "wrap the shirt around the hand, put the hand through the window" would work well enough.
Mythbusters did an episode about this whole myth in fact. It's on YouTube - check it out