Crew changes cannot be made everywhere in Greece. Only in Athens, Corfu, Kefalonia, Zakynthos, Lefkas, Syros, Rhodes, Kos, Kalymnos, Samos, Patmos, and Mykonos. The boat must be at the port or on anchor at the location where the immigration process is happening. For example, the boat cannot be in Paros Island and her crew to embark or disembark in Athens.
In Non-EU crew member disembarkations, the disembarking crew must repatriate, thus an air-ticket to their home country is required. The non-EU crew members to be embarked in Greece, must be arriving from a non-Schengen area. EU crew members can come in Greece to embark, or fly to anywhere they like when they disembark, or even stay in Greece, but they also must pass through the embarkation/disembarkation process at the immigration office