I am from Canada. I am booked on a cruise from Athens to Istanbul. All cruise passengers will be disembarking at Istanbul. Once I leave the cruise ship on day of disembarkment, I will be departing Istanbul immediately and flying to Athens. Will I need to apply for a tourist visa upon arrival at Istanbul in order to visit the tourist attractions there and will there be a problem when I try to leave Istanbul after I leave the ship for a flight back to Athens if I don't have a tourist visa?