Long Island Sound is an estuary, a place where saltwater from the ocean mixes with freshwater from rivers draining from the land. Unlike most other estuaries, the Long Island Sound has two connections to the ocean—the East River and New York Harbor on the west and a deep, narrow gorge called "The Race" on the east. Twice a day, 25 billion gallons of water rushes in and out of the Sound through The Race with the incoming tide. Ninety percent of the Sound's freshwater comes from three rivers—the mighty Connecticut, Housatonic, and the Thames. The Connecticut River reaches all the way up to Canada!