The Muyil River Float at Sian Ka'an is one of the most tranquil things I experienced in Tulum. A local tour guide takes you on a boat over the turquoise waters of the Chunyaxche freshwater lagoon and shows you around the ancient Mayan temple "Ixchel," which is made of limestone and built around 1100 AD.
You then hop into the refreshing and slow-moving water of the Muyil and float slowly down a canal that is tucked away from the harsh rays of the sun. When you reach the end, the boat meets you and brings you back to where you started.