The following 90 minute report
Investigative Reports - Chappaquiddick with Bill Kurtis explains the following as posted on the youtube site:
The reason Teddy didn't try to save Mary Jo Kopechne was because she was by herself when she drowned. Teddy left her in the vehicle upon seeing a police vehicle approaching, got out to walk back to the party, having told Mary Jo to turn around and drive back. In addition to being inebriated, Mary Jo had no concept of what that part of the road was like, and when she drove at that late hour, she turned into the water and went down with the vehicle. We don't know what Teddy would have done were he close to her location and knew she had gone under with the vehicle, but it doesn't matter since that was not the case.
Chappaquidick
https://www.youtube.com/watch?v=1DI_IZ61Ulk
If, Mister Bat Guanno, after watching this you still wish to insult me with your statement:
You have just proven that you are a fool, then at least you will know what I am referring to, although it won't resurrect the manners you evidently weren't raised with.