Car underwater

Say you were stuck in a car at the bottom of a lake.  What would be the best way to get out of it?  Can you just open a window, wait for the water to fill it up and then swim out?  Where would all the air go?

>>10
How would you open all of the windows if you were still in your seat belt? I guess you are assuming that OP has power windows, but those would likely be shorted out due to the contact with the lake water.

Why would you wait until the car was on the bottom of the lake before trying to get out? Seems like the better idea would be to get out before the car reached the bottom.