Finding yourself in a dangerous, and potentially life threatening, situation could happen to anyone thus knowing the essentials of how to escape from such situation is crucial, such as this tutorial on how to escape from a flooding vehicle.
Seemingly simple task, this extremely dangerous situation requires calmness and fast reaction. If you ever find yourself in such situation, the most natural thing you would do is to try and open the door right away, but this would cause the flooding vehicle to sink in faster thus lowering your chances for survival. Once the vehicle hits the water, you would have some reaction time hence it does not sink in immediately due to the air trapped inside the car. First and foremost option is to open the window of your door slowly and try to get out from it.
But be aware of the air pressure which is pushing on the door and the windows which might stuck your window. If this is the case, you would have to break it. Even though is big and you could easily get out, do not try and break the windshield hence it is built to resist impacts. Aim for the side windows instead!
Use your foot to hit as hard as you can at the top of the window, you could also use the headrest from your seat and jam the windows as hard as you can. After breaking it, take a deep breath of air and swim back to safety. But remember, stay safe and drive carefully!
Finally, check out this crazy Honda motorcyclist riding in floods.