Deer Island is absolutely the best shore diving around your area, can be lots of current though so must be dove with experienced locals, and usually at slack tide. Closest to you is probably Eastport ME which has a beautiful shore dive at the Old Pier site, it also must be done at slack tide. Mack at Navy Island is not sure on charters until maybe Jun-Jul. Join NB Divers (go to nbdivers.ca) to hear about organized upcoming dives, or look for a dive buddy!
Last time I dove Greens Point (a few years now) it wasn't looking so good.. fish pens near the site has made a silty mess.
For shore sites with less tidal concern, there would be Wallace Cove @ Blacks Harbour (can be silty), and Beaver Harbour. Also New River Beach towards SJ is a favourite local training site, it's just bad after heavy rain due to fresh water run-off (and is best around high tide as the walk can be long!). The Dive Shack (in SJ) organized some weekend dives last summer with a DM and I'm hoping they are doing that again this year.. great if you are new to diving or the area.
You can look on nbdivers.ca though for some of these site profiles.
We are planning a Victoria Day weekend diving/BBQ in May on Deer Island, might be a good chance to meet up with others and see some of the sites. You'll have to post on nbdivers if you need a buddy though, most are coming as part of dive groups.