A dogfish maybe. The chance of having an encounter with a dangerous shark in Maine is about as good as they chance of finding water warm enough to swim in. I would think your chances are a lot better (or worse I guess) down on the Vineyard and thereabouts.

We did see as HUGE fish once up in Quahog Bay while PaulD was visiting in his dinghy. I saw the thing and was so speechless I couldn't get the words out before the creature swam off.