The Nafplion Port Authority and Patras Port Authority can advise you about entry and exit in their ports for yachts. Patras's tourist office is at the port.
The Martha runs five times weekly in winter and daily in summer between Gythion, Neapolis, and Kythera. In the Peloponnese, call the local port authority for the latest information on boat travel.
Hellenic Seaways high-speed car ferries sail four times daily in summer from Piraeus to Porto Heli (two hours; about EUR 23); you can purchase tickets online. In winter the schedule is much reduced.
Hellenic Seaways (August 25, Heraklion, Crete. 2810/346185. www.hellenicseaways.gr). Nafplion Port Authority (27520/27022). Patras Port Authority (2610/341002). Piraeus Port Authority (210/422-6000).
Port Authorities (27330/22262 in Gythion; 27210/22218 in Kalamata; 27210/23100 in Pylos; 27320/61266 in Monemvassia).