AAA estimates that, every year, more than 10,000 drivers swerve off the road and end up submerged in water. This terrifying scenario can be life-threatening, as the water pressure exerted against a sinking auto makes it extremely difficult to open a door and swim to safety.
In a MythBusters episode Jamie Hyneman and Adam Savage took the plunge to verify the scientific logic that until a car completely fills with water and equalizes the pressure inside and outside it. As an engineer you can investigate this without having to sink a car, in a pool (though that might be more fun). Assume that the car sinks straight down with the front end first (i.e. car oriented vertically). Note this is different from the MythBusters who sank their car oriented horizontally. Calculate what at what depth a person will no longer be able to open the door of their vehicle while the passenger compartment is still filled with air. This question is highly open-ended. You will need to make assumptions to make the problem tractable. Justify your answer, including any assumptions that you need to make in order to solve the problem.