Cobscook Bay is located in Washington County in the state of Maine. It opens into Passamaquoddy Bay, within the Bay of Fundy. Cobscook Bay is immediately south of the island city of Eastport, the main island of which (Moose Island) straddles the two bays. In the 1930s, Cobscook Bay was part of the aborted Passamaquoddy Bay Tidal Power Project (a.k.a., Quoddy Dam Project) to generate electricity from its large tidal range.