Hydrais one of the Saronic Islands of Greece, located in the Aegean Sea between the Saronic Gulf and the Argolic Gulf. It is separated from the Peloponnese by a narrow strip of water. In ancient times, the island was known as Hydrea (Υδρέα, derived from the Greek word for "water"), a reference to the springs on the island.
The municipality of Hydra consists of the islands Hydra (area 52 km2 (20.1 sq mi)), Dokos (pop. 18, area 13.5 km2 (5.2 sq mi)), and a few uninhabited islets. The province of Hydra was one of the provinces of the Piraeus Prefecture. Its territory corresponded with that of the current municipality. It was abolished in 2006.
There is one main town, known simply as "Hydra port" (pop. 1,900 in 2011). It consists of a crescent-shaped harbor, around which is centered a strand of restaurants, shops, markets, and galleries that cater to tourists and locals (Hydriots). Steep stone streets lead up and outward from the harbor area. Most of the local residences, as well as the hostelries on the island, are located on these streets. Other small villages or hamlets on the island include Mandraki , Kamini, Vlychos, Palamidas, Episkopi, and Molos.
Hydra depends on tourism, and Athenians account for a sizable segment of its visitors. High-speed hydrofoils and catamarans from Piraeus, some 37 nautical miles (69 km) away, serve Hydra, stopping first at Poros before going on to Spetses. There is a passenger ferry service providing an alternative to Hydrofoils that runs from Hydra Harbor to Metochi on the Peloponnese coast. Many Athenians drive to Metochi, leave their car in the secure car park, and take the 20-minute passenger ferry across to Hydra.
Rubbish trucks are the only motor vehicles on the island, as cars and motorcycles are not allowed by law. Horses, mules and donkeys, and water taxis provide public transportation. The inhabited area, however, is so compact that most people walk everywhere.
Hydra benefits from numerous bays and natural harbors, and has a strong maritime culture. The island is a popular yachting destination and is the home of the Kamini Yacht Club, an international yacht club based in the port of Kamini.
In 2007, a National Geographic Traveler panel of 522 experts rated Hydra the highest of any Greek island (11th out of 111 islands worldwide) as a unique destination preserving its "integrity of place."