Before the arrival of water-skipping hydrofoils on the choppy waters of the Aegean, travel between islands was a time-consuming, stomach-churning experience. But now these modern vessels cut travel time and (usually!) provide a smooth trip.
The hydrofoil lines depart from the port of Zea, part of Piraeus near Athens, and Raphia/Rafina, a short trip from Athens. Remember that hydrofoils and catamarans don't run in late fall or winter.
Generally, the pace of life in Greece is languid, with few people, other than the occasional taxi driver, pushing the clock. However, the hydrofoils are exceptions. These swift ships depart promptly, and on two occasions that I experienced, a little bit ahead of schedule. Be there at least 30 minutes ahead of time, and make reservations in advance when possible. In the event of rough weather, the hydrofoils may be cancelled. The rough trip I mention here was the last ship allowed to travel that day - the hydrofoil lines try to keep their reputation for smooth travel intact, but when Poseidon gets frisky, what do you do?
If you are travelling Greece with luggage, the hydrofoils are minimally accomodating. Expect to handle your own bags. Crowded voyages mean baggage stuffed in every corner, another hazard if the trip is a little rough.
For those prone to seasickness, be aware that these journeys are not always glass-smooth, at least on the smaller hydrofoils.
Rough water will make itself felt. You may want to avoid sitting in the forward cabin of the vessel on the old yellow Ceres vessels, particularly during late spring, early autumn, and whenever storms are in the area. Stay inside the broad, flat rear cabin.
The outside areas of the hydrofoil are very tempting if you have a still or video camera, but once the ship hits full speed, you may be at risk if you are outside.
Even when the water is relatively calm, the wind may be surprisingly strong. I spent a cold half-hour outside because I didn't think I could make it back into the cabin one-handed, and if I let loose of my camera, either the wind or the jolting caused by high waves that day were sure to smash it into the steel sides of the ship. I finally leapt through the open door when someone stepped outside, and my camera and I both survived as the ship lunged and I nearly tumbled into the open baggage hold.
The reward for these efforts is the smooth, powerful sense of flying on water, like some semi-divine mythical personage. The nickname "Flying Dolphin" is well-earned.
Larger hydrofoils offer amenities such as full bars and "in flight" movies. On a journey from Rafina to Mykonos, the movie was a film called "The Big Blue", which included many scenes of hydrofoil travel. It was surrealistic to glance at the television monitor, see speeding water, then glance out the windows beside the monitor, and see the same speeding water. Fantasy. Reality. Greece always seems to combine both seamlessly.
Hydrofoils are fun, efficient ways to maximize your time in Greece and spend your time on the delightful islands, not on the deck of a slow ferry.
With the competition from the hydrofoils, the ferries have upgraded and are faster than they used to be, but nothing can match the hydrofoils unless you leave the water entirely and take to the air for your travel.