It may happen that your car unexpectedly falls into deep water or is swept away by a current; many deaths are caused by drowning within submerged vehicles. However, there is a recommended protocol to escape from such a situation. What is foremost is that no matter how scary such an event can be, do not panic. Panicking will use up more oxygen and will slow your attempt to escape.
Step One: Brace for Impact
If can see that you are headed into water you can prepare. The force of hitting the surface might set off your airbag system and so you must be ready. Keep your hands in a horizontal position on the steering wheel to prevent injury as otherwise the airbag might push your hands into your face.
Step Two: Remove your Seatbelt
Undo your seatbelt buckle in order to give yourself room to maneuver, since the seatbelt anchors you to the sinking car. If your buckle is jammed hold your seatbelt cutter securely and with a swift motion cut your seatbelt vertically. If you have children in your car, remove your seatbelt first and then that of the oldest child, who can help the others in the backseat. Instruct them to remain calm and keep breathing normally until the water is chest-level.
Step Three: Open the Window
It is better to open your side window to escape rather than the door for various reasons. Opening the door lets water flow in far quicker and makes your car sink faster, especially if the window is still above the waterline. Also, the water pressure makes opening the door difficult until the car is completely filled with water, which adds excessive risk. If your power windows stop working firmly strike the glass near a corner with your window hammer. The onrush of water should not prevent you from climbing out of the cabin.
Step Four: Exit your Vehicle
Exit arms first; the windows of cars are made with safety glass and are not dangerous when shattered. Push yourself out of the window and do not kick until clear to prevent hurting other passengers. If there are children in the car help them leave the car first. If you have an infant or toddler use the "teddy bear hold" to carry the child to safety. If you have a pet in the car that can swim, such as a dog, help it get out of the window and it will swim to the surface on its own.
Step Five: Swim to Safety
Swim to the surface as quickly as possible. If the water is murky your flashlight can help you find your way; air bubbles will always rise up. Be wary of objects around you and use floating or fixed supports to help get to the surface. If your car had fallen through ice look for the hole it made. Reach solid ground as quickly as possible and check for companions. Try to keep warm and call or signal for help. If your phone stopped working and there are no passersby then use your flashlight to shine a SOS signal toward where you expect help to come.