Last evening we had friends visiting from out of town, and they wanted to eat at a seafood place that was on the water, but not too expensive. It was raining, so the outdoor tables at J's Oyster Bar were unavailable (indoors was too smoky/loud/crowded). We ended up at the Porthole, on Custom House Wharf, near the Harbor Fish Market. It used to be a breakfast/lunch counter for fisherman, and has been slicked up, but not much. Funky decor, casual service, but really good seafood. I had mussels in a sweet/spicy broth with chunks of fresh tomato, and they were some of the best mussels I've ever had. Others in our party had grilled salmon, risotto with crabmeat, and pasta with mussels & shrimp--all were super and moderately-priced.