If you've already hunted divers on big water, I'm sure you're aware of safety concerns with a 12' boat. With that said, I'm sure if you pick your days and locations you could do well.
As to availability of the shoreline, I would recommend paying the town office a visit and glancing through the tax maps to find out who owns the shoreline you wish to hunt. If there aren't many houses in the area, the owners might be very agreeable. We have laws here in Maine regarding mean high tide lines and access rights for fishing and fowling, but I still think you're better off to ask the owner of that stretch of the shoreline. When I first started ducking, I used to ask myself the question a lot, "Is this area legal?" rather than "Are the landowners o.k. with me being here?"...I think the latter will save you a lot of frustration in the long run.