A wonderful fast and efficient ferry service throughout the main islands of Greece from Athens. See their web site for timetables, prices and tickets.
Most travel agents will sell tickets for Blue Star Ferries.
The high speed Catamaran makes a once a week trip from Rhodes to Kastellorizo. The day can change from year to year, so always double check on their web site.
High speed Catamaran based in Rhodes for ferry services around the Dodecanese Islands.
From Rhodes to Kos, Kalymnos, Leros, Symi, Lipsi, Patmos, Chalki, Tilos, Nisyros, Panormitis, Agathonisi.
Their web site has full timetables to all their destinations.
Tickets can be purchased at most travel agencies.