Great South Bay

Great South Bay is an arm of the Atlantic Ocean, approximately 45 mi (72 km) long, forming a large natural harbor on the southern side of Long Island in the U.S. state of New York. It is protected from the open ocean by Fire Island, a barrier island approximately 30 mi (48 km) long, as well as the eastern end of Jones Beach Island. The bay is accessible from the ocean through the narrow Fire Island Inlet between the western tip of Fire Island and the easter tip of Jones Beach Island. The bay connects to South Oyster Bay on its western end.

In the early mid-17th century, European settlers arrived among the native Merrick and an international horde of Freeport pirates, privateers, freebooters and their ilk, including the legendary Blackbeard and Captain Morgan.

Rapid suburban population growth on the northern shore of the bay has led to the bay becoming a population destination for yachts and other pleasure craft. Development around the bay has led to a degradation of the bay's water quality, and to the rapid growth of eel grass.