[xzins]

It wasn’t a deep pond. It wasn’t far to shore. Why was she not able to exit the same way as Teddy? The car wasn’t that badly damaged. She was at the air pocket.

I’d say she was disoriented and panicked. The air pocket proves she was alive for some time.

She was definitely able to be rescued.

[crunk]

These articles speculate that Mary Jo was curled up asleep in the back while Ted and another woman were in front. They could have escaped through Ted's open window. It's possible, I guess. Yet, you'd think the identity of the 2nd woman would have been exposed by now.

http://tomroeser.com/blogview.asp?blogID=24593

http://dailysally.blogspot.com/2006/01/my-ted-kennedy-chappaquiddick-story.html