Dark Harbour at Grand Manan is a natural saltwater pond formed by the tides, and surrounded by one hundred metre cliffs of columnar volcanic basalt. Fish farming occurs in centre rings of the harbour, and the area is also known for its world-famous dulse.
Make sure you time your visit for low tide, as the beach and access road are almost entirely submerged at high tide. To get a good view of this unusual but highly photogenic landscape, take the 2-3 hour hike from the working dock to the ocean inlet and back, but note that it is not advised to cross the channel (currents and undertow are strong). Best area to park is near the main working dock (as this area is always above water).