Hello - I will be traveling to three islands during August: Santorini, Ios, and Mykonos. As this is the busiest season, I'm wondering what the best way is to book ferry tickets between these islands and to/from Athens. I have seen some online reservation forms, but they all require a pretty steep charge to mail the tickets to the US. Is it best to have the ferry tickets already before the trip? Should we get them from an agency once arriving in Athens? Is there a better way to do this? I just want to make sure we'll be able to get onto certain ferries because our accommodation will already be booked ahead of time (again because of the busy season). Thanks!!