HI i am travelling to Santorini from Piraeus on 16th August 2014, which is a saturday. I am just so confused with the number of options they show while booking the tickets. Firstly should we really book in advance or a last minute booking is fine too. This being the peak season, will the ferry be sold out if we book last minute. ANd what is the difference between the VIP Lounge, Cabin - 4(external) and (internal).