Tankah is the kind of beach Tulum used to be twenty years ago. A small bay ten kilometres north of the ruins, the road in is unpaved, the cabañas are simple, and the swimming is direct from the sand: a coral reef begins about thirty metres offshore and runs the length of the bay. Snorkelling here is excellent and free — the reef is in better shape than the one off the main Tulum beach, and you will see tropical fish, fan corals, sometimes a turtle.
The bay also holds a small cenote, Manatí, where freshwater seeps from the limestone into the sea. There are two or three modest restaurants behind the beach but no nightlife to speak of. Quietest in the morning, before day-trippers from the Tulum hotels arrive.