Journey into the theoretical.
At 150 feed or about 5 atmospheres of pressure, the original air in the car should be about 1/5th the original volume. This would be assuming that when water had finished pushing in around every door and window gasket to eqalize pressure, it then leveled out and left the gaskets capable of keeping the air in the car. (No air would escape while the water entering with much greater force) So perhaps? the driver had air from neck level to the roof of the car and interior to exterior pressure had been equalized. He could then take a breath, open the door, exit and head to the surface while exhaling. Exposure to breathing at depth too minimal for the bends.
Don't want to try this myself, but it seems potentially plausible.!?
If anyone thinks he opened the door and escaped prior to reaching the bottom, I disagree. While the vehicle was sinking, the exterior pressure far exceeded the interior pressure making the opening of the door quite impossible.
Only other theory I can think of would have the driver escaping the vehicle as soon as it hit the water meaning he was driving an Aston in the rain with the window open or had time to open the window before impact. Seems far less likely than where I started trying to match the reported facts.
Theories, I love that game.