Oak Bay is the northernmost section of Passamaquoddy Bay, into which the St. Croix River empties. Its extent fluctuates with the Bay of Fundy tidal changes, so that its northern section changes from approximately 30 feet (9.1 m) in depth at high tide to exposed ocean floor at low tide.
Map of Oak Bay, NB, Canada
Oak Bay has a unique pool and manmade estuary caused by the creation of a causeway on Route 170. As a result, the easternmost section of the waterbody was split from Passamaquody Bay, connected only by four culverts which prevent the water from completely emptying during tidal changes. This pool is also fed by a small freshwater river on its northeastern border and thus experiences only a relatively minor height difference.
Located in the centre of the bay is Spoon Island, so named because of its resemblance to an overturned spoon.