Casa Cenote

The water here runs the wrong way for a cenote. It is a long channel lined with mangroves in Tankah Tres, north of Tulum, that flows underground for about 90 metres and comes out as a spring roughly 18 metres off the beach, so fresh and salt water mix and the fish range from cenote mollies to bigger sea species. Its other name, Cenote Manatí, is for the manatees that used to swim in; they rarely turn up now.

Think swim and snorkel spot more than cave, with shallow passages under the mangrove roots, and beginner divers do their first cavern tries in it. A small hotel and beachfront restaurant sit between the cenote and the sea, rent snorkel gear, kayaks and paddleboards, and run introductory dives. The restaurant closes before seven, and lunch is its busy hour.