I am Italian, from Venezia, and sail regularly around the Peloponnese to reach the Aegean Sea. From Kalamata up to Zakynthos, unless you have already visited these locations, I would consider:
-Anchoring in Methony Bay or mooring
strait into Pilos small port in Navarinos Bay. Like most Greek ports
, Pilos is free of charge. Do not moor in the main port: sometimes there is an annoying swell and bad smell from city sewage, go into the small port (the one called "marina" in most maps).
-Another small leg up to Kiparissia on the Peloponnese coast, about 27 NM from Pilos. This also is free of charge and out of the main touristic locations.
-From Kiparissia you can go directly to Agios Nikolaos, a small port on the north east of Zakynthos, again free of charge. Quiet and very pleasant. As already mentioned it is open to NE so if winds form that direction you may face an annoying swell, but in this case you can anchor SW of the small island at the entrance of Agios Nikolaos, still about 50 m from shore. If no winds/sea from NE, moor in the port, at the concrete pier ESE, the one facing the petrol station. It is owned by the family
of Dimitris, a nice young fellow. He offers the mooring
and electricity (if needed) asking that the guests take dinner at his restaurant (near the petrol station), fairly cheap
and delicious lamb ribs...
I would avoid Zante port: large, noisy, smelly, with swell caused by ships, although may is low season.
-On the NW of Zakynthos you have the famous wreck bay. You can pay a visit to it and then overnight at Vromy Bay, about 3 NM south.
-Continuing north for Levkas, I would consider a stop in Samis port (Kefalonia Island). Here the port authorities ask for a small fee. Than continue north along the canal between Kefalonia and Ithaki and spend a night anchored in one of the beautiful bays before Fiskardo, like Palaiokaravo.
-Last but not least, pass by Fiskardo, the VIPs village of Kefalonia, and from there you are close to Levkas...
SV Albin Vega