Clark Cove is considered part of Hummock Pond and is considered part of a Massachusetts Great Pond. Clark Cove, sometimes called West Hummock Pond, is surrounded by conservation land and receives very few visitors most of the year. This is probably the quietest and cleanest pond on Nantucket.  This is a freshwater pond that the town does not open to the ocean. Clark Cove reaches northward between the west side of Sanford Farm and the east side of Head of the Plains. These properties are owned by the Nantucket Conservation Foundation and the Nantucket Islands Land Bank.  See below for information.
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 Once part of the hook-shaped Hummock Pond, Clark Cove became Hummock Pond’s little brother during the Blizzard of 1978. During that storm, the ocean ate into the beach in front of Hummock Pond, eroding it enough to temporarily open it to the ocean, and then pushed sand inland, permanently closing off Clark Cove from West Hummock Pond.

The AllTrails website has a description and map of a hike at Clark Cove.