I tend to do better on the NS, although there are very good spots down here as well. The things is parking is even more restricted on the SS, so there are not that many good accessible shore dives, but, two spots worth going are:
Brant Rock in Marsfield - just down the street from NAS dive shop
Gunnrock Beach in Hull - also a great night dive spot
Public parking at both places, brant rock is shallow, but, it's a huge area to work, gunnrock is a little deeper with a max around 40'.
Off season - Pegotty beach in scituate is nice too, just don't go near the "Forest Queen" end or residents will think you are "looting" the wreck (ie. it's totally enrusted remains) and call in the calvary.
I do alot of free diving for lobster around Cohasset, but, again lots of the sites are no parking (even for residents) or no tresspassing.