At the mouth of Marblehead’s Little Harbor is a small island that is managed by the Trustees of Reservations, like its neighbor, Crowninshield Island.  When the tide is very low, you can walk across the tombolo to explore its rocky shores.  Just make sure you plan your visit so you return before the tide comes in again.

For more information on Gerry Island, see:

https://thetrustees.org/place/gerry-island/