I've never dove Beseck...but I wouldn't. It is a VERY small "lake" with lots of boat/jetski traffic. I've been out on the lake before, and wasn't terribly impressed with water quality. A Lot of weeds too.
Candlewood is decent, but very silty and a LOT of boat traffic. Dykes point is an OK entry point. Last time I dove there I swore I would never do it again.
There is a site in Norfolk called Westhill Pond. I've never dove there before, but I've heard good things about it, good vis, lots of fish, not a lot of boat traffic. You can check it out here:
http://dep.state.ct.us/cgnhs/lakes/westhill/Lake.htm
The only negative thing, is that the greatest depth is in the middle of the lake, and to get there you would need some type of boat to dive from. They allow boats with engines up to 7HP on the lake, but you could easily get there from a non powered boat, and I think they rent them there.
Other than that, there isn't a whole lot other than the Portland Quarry which is underway (see other posts in this section). That will be a DREAM come true when that is up and running!