There are a few Legal Seafoods in Boston, and many up and down the coast. For locations/addresses, go to www.legalseafoods.com and click on locations.
This was the first place we decided to go after we left the airport. We didn't really have to wait very long. For an appetizer, we both had clam chowder—I would definitely recommend it while in Boston. For a main course, I had a small order of lobster, and my father (who I was dining with) had a shrimp trio platter with three different types of shrimp, coconut shrimp being one of them.
All of the food was very good but kind of pricey, definitely a splurge. You will notice that they really do want you to enjoy your food here, as they will ask you if everything is good about every 10 minutes. I would recommend this restaurant if you are looking to enjoy some quality seafood while in Boston.