Central Long Island Sound is deeper than regions to the west, with a channel, and the tidal range is reduced but tidal currents are more developed, with moderate flushing. It has a muddy to sandy bottom. The bottom waters are generally more oxygenated. The water is clearer in Central Long Island Sound. The land use surrounding this area is suburban to rural, but the development is less dense. There is a significant input of treated wastewater to this area from Connecticut, and largely septic discharge from Long Island. The watershed draining into Central Long Island Sound includes the Housatonic River, other small coastal rivers in Connecticut and a few small embayments and a sand bluff shoreline of a narrow undeveloped portion of Long Island.
This reporting region extends from Western Long Island Sound to a line extending from Roanoke Point on Long Island to Pilots Point just east of the Menunketesuck River. Central Long Island Sound forms the northern boundaries of Port Jefferson and Miller Place Harbors on Long Island and Bridgeport Harbor, Housatonic River, New Haven Harbor, Branford Harbor, Guilford Harbor, East River and Clinton Harbor on the Connecticut shoreline. There is a clockwise residual water circulation in this region.