There's plenty of innuendo about Chappaquiddick, but what, exactly is the evidence? From what I've read about it, the only crime Kennedy can be convicted of is leaving the scene of an accident; which is the crime he was, in fact, found guilty of. Was he drunk? You don't know and I don't know.
Mary Jo Kopechne would have been just as dead no matter whether Kennedy had called the cops as soon as he possibly could after the accident or not. Was his behavior after the accident what he would, in retrospect, wish it to be? Of course not. Is it plausible that it was the result of the shock of the accident itself? If you've ever been in a car accident, you'll know that that that is perfectly plausible. Lots of people find themselves in something of a fugue state when they've had a great shock--not really able to process information in normal ways.
So...that's about what you've got. The guy had a car accident in which a passenger died and he behaved weirdly for about 20 hours or so after the accident. He was duly punished by the state for his weird behavior.
The hilited portion suggests that your reading about Chappaquiddick seems to be restricted to Kennedy press releases.
"The diver, John Farrar, later testified at the inquest that Kopechne's body was pressed up in the car in the spot where an air bubble would have formed. He interpreted this to mean that Kopechne had survived for a while after the initial accident in the air bubble, and concluded that
“Had I received a call within five to ten minutes of the accident occurring, and was able, as I was the following morning, to be at the victim's side within twenty-five minutes of receiving the call, in such event there is a strong possibility that she would have been alive on removal from the submerged car."