No problem, sorry I haven't been 2 Dia so I could tell U about that as well. I figure it's about the same on the boat, but since Dia is an island I think there is some kind of guided tour, beaches & maybe some watersports there once U arrive the island...
Maybe some1 else has been 2 Dia & can help us out here!?!
Anyway, enjoy Ur holiday.
(I can't WAIT 2 go Hersonissos myself, exactly 1 week left 2day! )