The premier shore dive site in Maine is the Old Steamship Pier in Eastport. The site is the remains of an old steamship pier used by Franklin D. Roosevelt and others. Campobello Island, Canada can be seen right across the way. Currents at this site can be strong due to tidal differences in excess of twenty feet, after all this is the Bay of Fundy area. Marine life is prolific and immense due to high nutrient flow from the currents and tides. Being the site of an old pier and fishing town there is ample opportunity to gather old medicine bottles, clay pipes and other antiquities long ago cast in to the sea.
The only down side of the site is that it is a long way from "civilization". It is over a six hour drive from Boston.