On a recent summer day, we took a trip out to the Boston Harbor Islands. Last summer, we spent a long and lovely day at Odiorne Point State Park at the tide pools. Spectacle Island also has a great spot for finding sea animals and is a quick boat ride away.
Make sure you buy your ferry tickets before you go. The view of Boston from the boat is worth the trip alone. And, make sure to pack a sweatshirt because it's a windy ride.
Spectacle Island is small so it's very easy to navigate. The tide pools are a short walk along the beach to your left as you exit the boat.
The hunt to locate crabs and mussels was a blast. My kids got so excited when they lifted a rock to spot a few crabs. We even saw female crabs with eggs.
Make sure to bring a bucket if your kids want to collect some shells to take home. We let all of the crabs and and mussels go before we left so that they could stay in their natural habitat.
We found this article by MommyPoppins.com to be really helpful before we went: http://mommypoppins.com/content/visiting-the-boston-harbor-islands-with-kids-15-things-to-do-on-spectacle-island