There are plenty of options to choose from, but one of the most famous is the Kas-Kekova Boat tour.
Kas is a cute town on the Turkish coast, known for its beautiful turquoise bays, and the best way to explore some of them is by going on a boat tour.
Expect scenic views, lots of swimming and jumping in the turquoise water (seriously, the color of water here is crazy), sunbathing, and learning a bit of the history of the Kekova area while admiring the ruins.
Some of the places you visit: - Inonu Bay - Aquarium Bay (lunchtime) - Simena Castle - Yaglica Bay (Pine Bay) - Sunken City of Kekova - Sunken City of Theimussa