Long Island Sound is a tidal estuary of the Atlantic Ocean, lying predominantly between the U.S. state of Connecticut to the north, and Long Island in New York to the south. From west to east, the sound stretches 110 mi from the East River in New York City, along the North Shore of Long Island, to Block Island Sound. A mix of freshwater from tributaries and saltwater from the ocean, Long Island Sound is 21 mi at its widest point and varies in depth from 65 to 230 feet.