Gardiners Bay is a small arm of the Atlantic Ocean, approximately 10 mi (16 km) long and 8 mi (13 km) wide in the U.S. state of New York between the two flukelike peninsulas at the eastern end of Long Island. It is bounded on its eastern end, where it connects to Block Island Sound, by Gardiners Island and Promised Land. Gardiners Bay is part of the Peconic Estuary and received the designation as an Estuary of National Significance from the U.S. Environmental Protection Agency in 1993.