The harbor of Fourni gets a fair amount of swell with the `meltemi (the Etesians)` and to compound the problem its rocky bottom with a thin layer of mud provides poor holding.
The best place for a yacht is alongside the southern side of the ferry jetty at the SE side of the harbor, where there is space for two yachts to raft up, or (if a ferry is not parked there) alongside the northern side of the same jetty.
Occasionally it is possible to moor for short periods on the inside of the harbor breakwater, where the fishing fleet berths, although you may be asked to move if a fishing boat wants the space.
Yachts sometimes anchor moor on the outside of this breakwater, but this should only be attempted in very settled weather as berths here are completely open to the NW.
Warning: Be aware that a large Hellenic Seaways ferry now calls at Fourni several times a week, arriving at 0500 and sending a minor tsunami into the harbor. If you are alongside the ferry jetty, the port police will ask you to move off temporarily for your own safety. Take their advice!