Saint Thomas, United States Virgin Islands in the context of Hassel Island, U.S. Virgin Islands

Water Island (Danish: Vand ø) is a minor island in the United States Virgin Islands, an American territory located in the Caribbean Sea. The rest of the U.S. Virgin Islands were acquired by the Americans in 1917 from Denmark; however, Water Island was excluded, thus the Danish East Asiatic Company, and by proxy the Danish kingdom, continued to own Water Island until several decades later. Water Island was bought by the U.S. Government in 1944, and in 1996 it was transferred to the U.S. Virgin Islands. The island is of volcanic origin and lies to the south of Saint Thomas in the Charlotte Amalie harbor. A ferry service runs regularly from Crown Bay, Saint Thomas, to Phillips Landing, Water Island; the ferry ride is about 10 minutes.

At 491.5 acres (1.989 km) in size, it is administratively part (with Hassel Island) of the subdistrict of Water Island, in Saint Thomas District. Water Island is a residential island, with a population of 182 (2010 census) and no significant commercial establishments. A number of homes on Water Island are available to accommodate visitors. The main attractions are beaches, including Honeymoon Beach, plantation ruins, Fort Segarra, an underground fort partially constructed by the U.S. during World War II, and scuba diving site Supermarket Reef in Limestone Bay.