In an emergency with a vehicle going into the water, you only have seconds to act. Maybe someone cuts you off while you're driving near a river, for instance. You swerve to avoid them, make contact anyway, and lose control of the car. It winds up in the water.
You don't have time to think. Do you know what to do?
First off, remember that the power is going to fail. If the doors weren't already unlocked, do it immediately. If you have power windows, roll them down. The same is true for crank windows, but there's a bit more urgency with power since it may stop working.
If the power does fail and you can't roll the window down, take the headrest off of the back of your seat. It likely has two metal arms that clip into the seat. You can use them to break the glass. Always break the glass on a side window, not the front windshield. It's made from safety glass and won't break properly.
If you have kids with you in the car, unbuckle them from oldest to youngest. Help them through the window first. Tell kids who can swim to do so right away. If any cannot swim, give them something buoyant and instruct them to hold onto it. Help will likely come from the bank quickly if they can just stay above water.
After a crash like this, you could have serious injuries, even if you escape the car. Make sure you know how to get compensation for medical bills and other related costs.