Greek ferries and island hopping

The first thing to understand about Greek ferries is that "the ferry" is usually two different boats, and picking between them is the only decision most travelers actually have to make.

The fast boat — a catamaran or hydrofoil — is the one that turns a crossing into a short hop. The conventional ferry is larger, slower and cheaper, and on a given route the difference is not marginal. Piraeus to Poros runs about an hour on a fast boat and around two and a half on a conventional one, which on a short trip is most of a morning either way you decide.

The car is the other half of the question, and it is worth separating from the first. Conventional ferries carry vehicles; the fast boats generally do not. That sounds like an argument for the slow boat until you ask whether you want the car on the island at all. On a small island where the town is walkable, taking a car across buys you very little and costs you the slower crossing, the vehicle fare and the parking. Leaving it on the mainland and crossing on foot is frequently the better trade — at Poros you can leave it at Galatas, a few hundred meters away across the channel, and cross without it.

Work out whether the island even has an airport before assuming a ferry is a constraint rather than a choice. Several of the places people reach by boat have no airstrip at all, so the ferry is the route rather than the budget option; others are quicker to fly to than to sail to once you count the drive to the port.

Build slack around the crossing on days when you are also flying. A ferry is the leg most exposed to weather, and a tight connection between a boat and an international departure is the kind of plan that works until the one time it does not.