Canadians & American citizens:
If you are flying into or out of Turkey yes you need a VISA if you are flying into turkey you can get one at the airport .
If you are stopping on a cruise in Turkey eg: Ephesus
You do NOT need a visa
Went on Princess Mediterrean Cruise in June. Turkey was one of the stops, did not need Visa. Your ticket agent should be able to tell you if any of your stops need visas. It's very important, as I was told if one of your stops needs a visa, even if you don't get off at that stop, yyou will not be allowed to board the ship at embarkation without the proper papers. Good luck.