The electric window motors and locks will still work when under water, remember the water doesn't conduct its the impurities in water and compared to the wiring to the motor, its not a very good conductor.
However in the mythbusters test they found that while the window motors worked fine, they couldn't roll down the window due to the pressure of the water, even with the manual windows.
All the vehicles I've seen with electric locks they still have a manual lock on the door somewhere, so you should still be able to unlock and escape.
I've also noticed that the newer cars with the laminated windows the window track is no longer inside the door. Used to be the door frame was a U shape and the track sat inside it, now its more of an L with the other side being nothing but the track so it should be easier to push the whole window out, but that would still require the inside to be full of water to equalize the pressure.
Maybe the new side air bags should have a smaller explosive charge to break the window when the airbag deploys.