There is a fast ferry (Catamaran car ferry) to Santorini usually via Sifnos. The company that runs them is CALLED Hellas Flying Dolphins. I am afraid you have been mislead by people saying they are passenger only flying dolphins(hydrofoils), I have not seen them in the Cyclades for many years. There is no problem getting to Santorini there are around 4/day ferries in summer.

Brotherleelove, according to the Hellas Flying Dolphin website there is no ferry from Sifnos to Santorini no matter which dates I plug in, regardless of the month. I can't seem to get a response for Piraeus to Santorini either. Can you clarify? I must be doing something wrong. Could the route you mentioned be a summer-only addition to their normal scheduling?

http://www.forth-crs.gr/hfd/english/pgres.exe?PM=CR

I was in Athens in June of 1998. I know for a fact that there was/is a ferry/hydrofoil/boat from Piraeus to Santorini. A couple from Sydney that my friend and I met travelled there by one of these boats. My friend and I saw them off at the port of Piraeus. We were travelling to Hydra at the time. Couldn't you make travel plans at the last minute once you get to Athens? I am sure a travel agent in Athens could hook you up with getting to Santorini. I agree with those above who state that it is not wise to plan too arduously in Greece.

Don't give up hope.

There are plenty of car ferries from Piraeus to Santorini, that's not in question. I'm wondering about faster hydrofoil ferries, both passenger-only and full-service. I can't seem to find any references to them on the websites I've found. On the www.gtp.gr website the code for catamarans that carry both cars and passengers is "cc". When I look for ferries from Piraeus to Santorini all eleven of the ferries listed from three different companies (none of them Hellas) are designated "cf" which is the standard slower car ferry that carries passengers as well. I'm thinking that the "cc" and "hf" (passenger only hydrofoils) must be summer-only services that haven't been added to the list yet.

I recently stumbled across this page with the Hellas Flying Dolphin schedule for summer 2005. I haven't checked it out so you may want to verify things but I hope helps.
http://www.milostravel.gr/anaxoriseis/info%20HFD2.htm

Excellent, janaturner, thanks.

So I took a look at the website mentioned by janaturner and noticed that the summer hours begin on June 17, 2005. We will be there a week before that. Do you think beginning of June is still considered "Summer Hours" or will I have to go my the off season time tables??

It's all a bit confusing, isn't it? The trick is to have a little faith, keep flexible and hope for the best. Don't try to have every move arranged in your mind in advance or you'll never relax and enjoy yourself.

This website shows a different timetable for the Cyclades-Crete run by Flying Dolphin. It says Monday, Tuesday, Friday, Saturday and Sunday from April 22nd, and "Daily" from May 30th onward.

http://www.greekislands.gr/hfd/

I've also noticed that the www.gtp.gr website has now posted updated summer timetables.

I am also trying desperately to arrange our holiday. I have been to Greece before and not booked Ferries, however this time I am taking a family of 4, and have to pre-book accommodation.

I spend 3 weeks in Greece a few years ago. Took every mode a transportion available. Plane, train, hydrofoil, ferry. Just remember even just island hoping plan to spend a full day traveling. Nothing runs on time in Greece. Nothing!! So just go with the flow. Just realize that your ship that is suppose to leave the port at noon probably will not show up till 4. That said once we went with the flow it was the best trip I ever had. Oh, and sometimes they don't follow the sequence of islands they are suppose to go to. Have fun. Also just make your reservations when you get there. It is much easier.