Transport decides your days here, and it is the part most plans leave vague. Crossings run daily through high season, and you plan around the timetable rather than the mileage.
Arriving at Athinios
Ferries dock at Athinios, and the ride up to a cliff village is a separate leg with a driver rather than a walk. On a group trip, that leg is already handled. If you are booking it yourself, add the transfer when you reserve the room, so a late arrival does not turn into a negotiation at the dock.
Leave a buffer on the way out. Crossings here slip when weather or a strike interferes, and a same-day ferry-to-flight connection is the one piece of timing worth protecting.

Ferries Between the Islands
From June through early September, there are multiple departures a day between the main islands. Fast ferries cut a crossing to a few hours, while slower boats are cheaper and more scenic. For July and August, book ahead, especially between Santorini and Mykonos, where the pressure is highest.
Out of Athens, ferries leave Piraeus for both Mykonos and Santorini. Santorini also connects by sea to Naxos and to Crete, where the boat comes in at Heraklion. On the long legs, a short domestic flight is the alternative the ferry timetable cannot match.
The boat is the spine of any island-hopping week, and it is the part a travel guide to Santorini tends to treat as a detail. Two of the three trips on this page carry the crossings for you: the 7-day Athens, Santorini and Crete route and the 8-day island-hopping run through Tinos, Mykonos and Naxos. A Santorini tour that includes them takes the two hardest transfers of the trip off your hands.
Moving Between the Villages
The rim villages sit in a line along the cliff, and the excavation and the beach sit away from it, so a day that mixes both spends real hours in a vehicle. Group the days instead: one for the rim, one for Akrotiri and the water, one for the sunset you came for.
Keep the middle of the day loose. Ferries, transfers, and sunset crowd into the same late-afternoon window, and squeezing a swim into it is how people end up watching the light from a car.