Be aware about bookings with Hotel Atlantis in Naoussa, Paros. We were booking via their official website online and it turned out that the online given "booking confirmation" is not binding for them. After all payment details including credit card number and choosing from the hotels availability calendar the hotel was sending an email which combines their original firm "booking confirmation" with an unfirm "customer request" which has to be again confirmed by the hotel. When I called immediately after receiving that email Hotel Atlantis I was told that there is no availability.
Unfortunately in the meantime we had already booked our ferry to Paros and it turnout that there was no other decent available hotel room in Naousa (beginn of August!).
So we ended up with a big mass because the hotel is accepting legaly binding bookings even they have no availability.
As I am booking often via internet I am very careful how and with whom I am booking ... but against a fake OWN hotel website booking process I have not really any chance ... aside warning on tripadvisor...
NB: We ended finally up on Naxos island (same ferry)