We came with our greyhound as foot passengers 10 years ago. We took the ferry from Bari to Igoumenitsa, this being the shortest route at the time. Didn't want the poor dog to have to cross his legs for 24 hours! We booked an extremely clean 'pet cabin'. There are now pet cabins on the route Pireas - Chania. FYI, as a greyhound he was happy to be muzzled at all times, but we were asked endlessly "does he bite?", so maybe the muzzling requirement wasn't strictly enforced then. Don't know if it is now. Good luck!