That seems like mostly bad advice. What you should do is open the door as fast as possible, before the car has begun to sink. There's not enough water pressure

That seems like mostly bad advice. What you should do is open the door as fast as possible, before the car has begun to sink. There's not enough water pressure at that point to prevent it. If you freeze and hesitate then you're past the point of being able to just open the door unless you calmly wait until the interior has filled with water and then you can again. But at that point you're likely panicking