I was reading about the very same thing this evening. I was thinking that if I found myself in such a position in my own car, since I have both automatic windows and doorlocks, I might find myself in quite a pickle.
First I looked up how to get out of a submerged car and found some good info
here. Then I started looking at center punches, life hammers, and so on that might be small enough to EDC so no matter who's car I was in, I'd be better equipped for such a possibility.
The
ResQMe looks like a handy item with a spring loaded center punch, seatbelt cutter, and quick detach keyring.
There may be some other items out there like this, but I just started looking and don't know for sure. If anyone knows of a similar item, please post a link if possible.