Pretty sure in MA private property extends from the mean high water mark to the mean low water mark... Colonial Ordinances of 1641-47
** Should have been more specific- those ordinances allowed for public use of private tidelands for three purposes- Fishing, fowling, and navigation. So if you just want to go for a hike, you're outta luck. But if you have a fishing rod, it's perfectly legal.
Not sure about RI...
Ranting to angry homeowners about the aforementioned ordinances has generally worked for me in the past
