If your idea of a great vacation means being by the water, make tracks to Lovells Island. No matter what you choose to do here, you're unlikely to tire of those pretty views.
You'll need to find your way to Seaport District to reach this water-surrounded land mass. If you plan to do some sightseeing after you're done, why not stop by Fenway Park? It won't take long to get to from Lovell's Island.