I just got done watching UFO Files on the History channel.The topic was about the Shag Harbor incident.It was a very strange event.What shocked me the most was when the Soviet sub entered the harbor and the US Navy stopped it from investigating.What do you all think was at the bottom of the harbor?Another odd thing was the foam found on the water.Any comments on this very strange encounter?

It was strange I saw the episode as well.
As for the whole soviet thing I think that most likely the U.S did not want their sub to investigate because of the political climate of the time (it was during the Cold War).
I have no clue what the foam was.

I dont think the UFO crashed in the harbor, I think it just submerged and explored underwater and thats why no one could find anything.

It certainly is one of the more interesting cases (Canada's Roswell)...
Deserves a writeup all it's own really, as there is a ton of paper trail, witnesses, and necessary illustration. Feel free to beat me to it, as it's in my "eventual to do" pile...

I have been, and still am, watching the History Channel's UFO documentaries. I find them fascinating and well done. Not being a fanatic UFO believer, I find the History Channel's treatment of these topics refreshing and informative. Most shows are either "wooooooooo UFOs" or "Hahahaha UFOs". I find most of these shows well-balanced. They debunk what can be debunked and admit when they encouter things that can't be explained. I find these shows to be some of the best I've seen on this subject.

The "UFO Files" is probably the series in question, and yes, they are generally pretty well done. I was DVR'ing them to catch any I hadn't seen before during the marathon. The History Channel in general can be hit or miss on these though, with other UFO specials... all depends on the producers I imagine.