In MN, when we're driving on the ice in the winter to head out ice fishing or whatever - you're supposed to have all the windows rolled all the way down and seatbelts off (including kids in carseats) already.

You're already dressed for the cold and there's little worry of a car accident on the ice.

When a car goes through the ice, it's almost always the front end first while the back end may not break through. The nose tips down and slides in head first giving you time to dive out the window.

And usually the ice around the car while it's sinking won't let you open the doors at all anyway - let alone the water pressure.