It depends... To which island would you like to go? In winter, it is almost impossible; in summer, there are ferries from Winthrop, from Hull and from the Boston waterfront. Once you're out there, there's a water taxi that takes you accross from island to island. Check the website for ferry schedule and prices
There are ferries that take you to the islands.
Come to Deer Island. I work there. Its a beautiful island with a nice views. It will be better if visit in spring or summer.
You can walk Deer Island, which is connected to the mainland (Winthrop) via a causeway. World's End in Hingham is also part of the mainland. Georges, and according to the Boston Harbor Cruises web site Spectacle and Peddocks, are accessible year round. They are the carrier to contact. Keep in mind tbat they are federally administered and presumably inaccessible during the current shutdown.
Blue line aquarium station inbound. Subway
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