If I recall the story correctly, Ted Kennedy never called the police. They (the police) found the car the next morning. Kennedy had, by that time, swum over to the mainland, concocted a story with his "advisors," and returned as the police were pulling the car from the water and checking the license plate.
Anybody out there remember the details?
Here you go, enjoy:
http://www.ytedk.com/chappindex.htm