At the west western medieval sources - primarily geographical scripts and maps- the name of the island appears changed with different versions (Sidra, Sidre, Sidera, Sidro and others).
While it has not been made clear when the current name was established, Hydra remained almost uninhabited, from the second half of the 15th century though its settlement starts with the occupation from albania-speaking from the neighboring Peloponnesus. The disrupted conditions that prevailed at the 16th and 17th century and the concomitant lack of the security where the major reasons for the settlement to island of young families, albanian-speaking and greek, from different regions of the Heraldic and the asia minor region. It is period that the formation at the current settlement of Hydra starts, but also the setting of the ground for the latter on development of shipping, since the infertile soil of the island forced the habitants to turn towards the sea foe resources for their survival on of their well being.
During the 18th century the people of Hydra started engaging with building of small sailing ships (trehantiria) and from the middle of the same century ships of greater capacity, that sailed in the whole Mediterranean and the black sea. In parallel the war battles and rebellions of the Helladic region during the same century resulted to the setting to Hydra of new colonists from Peloponnesus that reinforced even more -in terms of population and economy- the island.
A series of reasons at the and of the 18th and the beginning of the 19th contributed to the acme of the shipping and commercial activity of Hydra and in effect to its financial and spiritual blooming: the possibilities that offered to the greek commercial shipping the turkish-Russian agreement of Kioutsouk Kaintazi (1774) the favoring of the Othomanic government, which was very much based on the naval experience of the people of Hydra that served the turkish fleet, the self government that the island managed to get and the region for the Turks and primarily the braking of the blockage that England has commanded to the ships of the French Napoleon for the transportation of grain, in combination to the disapearance of the French ships from the eastern Mediterranean. The high level of development of the shipping and commercial activity are proven by the establishment of the shipping school and the invitation of Italian and portuguese teachers for the effective teaching of the naval art, as well as the establishment of special laws and rules for the setting of relevant transactions.
Just before the revolution of 1821 the island had population of approximately 28.000 habitants and carried 186 ships, equipped with canons for dealing with the piracy and with very experienced to war crew. The revolution in Hydra was declared officially at the 16th of April 1821 from Antonio Economou and the people that broke the reservations of the first. The island contributed significantly to the naval efforts by sacrificing human lives, ships and money and bringing out leaders and fighters like A.Miaoulis, A.Tobazis, A.Tsamados, G.Sahinis, G.Sahtouris and many more. Great was also the reaction of the powerful people of Hydra to the effort of I.Kapodistrias to abolish the privileges that the island enjoyed until then. After the establishment of the Greek state and for almost a century Hydra, besides its small size and the prolonged financial decline, gave to the political life of the country five prime ministers, many ministers (especially at the hipping ministry) as well as the admiral P.Kountourioti, leader of the greek fleet at the Balkan wars and the president of the greek republic.
During the 20th century the habitants were involved more systematically with fishing and sponges collection, an activity that gradually came to a total decline and did not manage to slow down the financial and population deterioration of the island. From the decade of 1950 Hydra was discovered by artists and producers of movies and since then the island was transformed to a cosmopolitan tourist center.
Over the years the island of Hydras, which are part of the Saronic Islands in the Aegean, have experienced a steady rise in tourist arrivals in recent years with most of the visitors coming from the capital city of Athens comprising a large part of those who come over to visit. Tourism packages offering all inclusive holidays to Greece can include a trip to Hydra to visit its many bays and beaches as well as options for going on popular yachting cruises with the island's history of having a strong maritme culture and being an important port.