•Book your flight to El.Venizelos, the Athens International Airport
•You may use either train or bus to get from the airport to Piraeus.
--- Take the X96 bus to Piraeus. The stop is right outside the arrivals entrance at the airport. This bus runs day and night at about half hour intervals. Buy your ticket at the kiosk and then validate it in the machine on the bus. This bus will take you straight to the harbour in an hour or an hour and a half depending on the time of day. *)
--- If you choose the train: At the airport, go out and follow signs "To Trains". Buy a ticket for Green Line # 1 to Piraeus (terminal station). In Piraeus, use the main exit, turn to left and walk a few hundred meters to find the Dolphins. - More travel options and hints at http://www.hydradirect.com *)
•Take a Dolphin hydrofoil from Piraeus to Hydra. Book your tickets on-line at https://hellenicseaways.gr/en/ The route is Piraeus - Hydra and it takes about 90 minutes. Online reservations with credit card. (Summer 2017 schedule is not available before late Spring!)
•Connect with http://www.hydra.com.gr for hotel information.
•Connect with http://www.hydradirect.com for general information, accommodation info, culture news, local business etc
*) I'm copying a very useful message posted by CitizenKane in an older thread:
Attached is a map of the Pireaus port area in which I have pointed out the walking route and the following locations:
A - the terminal metro station Pireaus (Line 1, green)
B - the Hellenic Seaways office at Karaiskaki Square
C - the Gate E8 entrance/exit sign
D - the area where the boats to Hydra depart
E - the bus stop Karaiskaki Square (Bus X96, straight from the airport)
Your boat ticket should say the type of vessel and vessel number, for instance Flying Dolphin 19 (XIX). This number is also painted on the side of the vessel. Also, at the entrance to the vessel plates show to which destinations the vessel will go, for instance Poros, Hydra, Spetses, Hermioni etc. Oh, and don't forget to validate your metro/bus tickets (metro: machines at the entrance to the station/platform; bus: in the bus itself).