Green Canyon is not the sea: it is a vast freshwater reservoir created by the Oymapınar Dam, folded into the Taurus mountains inland from Manavgat. The water is a deep glassy green, the cliffs above it carry pine forest, and the temperature drops pleasantly the moment you leave the coast road behind.
From Belek the trip is a proper full day — around eight hours door to door. An air-conditioned transfer brings you up from your hotel, you step onto the boat at the jetty, and the itinerary alternates slow cruising beneath the cliffs with anchor stops where you can slip straight into the water.
A grilled lunch is prepared and served on the boat itself, so the day never has to pause; sun-lovers keep their spot on the open deck while everyone else finds shade. Non-swimmers are welcome — plenty of guests come purely for the scenery and the cool mountain air.