We were in Turkey in June on the Emerald Princess. The ship collected our passports before we arrived in Greece and kept them through our Turkey ports until we returned to Italy. In Turkey, they provided us with a printed generic passport - essentially we were in Turkey as a guest on the ship's visa. This is regardless of whether we were on a ship tour or on our own. We did not take any ship excursions and traveled on our own with no problems. It is my understanding that if you are arriving in Turkey by air or traveling by land for several days you must get a visa.
We loved Turkey, Have Fun!