I saw this vessel, the Maine Responder, in the harbor this week. I had not seen it before, so I looked it up to find that it is an environmental remediation and clean up vessel. It recently returned from the Gulf of Mexico, where it had been assisting in the oil spill cleanup.
Hopefully, this was just a stop over, and there was nothing spilled in Boston Harbor that needed cleaning up! (Although I did hear a rumor of a diesel spill in the area of Rowes Wharf last week).