The crystalline, sparkling blue waters of Cuatrociénegas are beautiful and very alluring. The town invites visitors to explore these aquatic treasures, but they are also highly protected. They are home to a diverse ecosystem of plants and fauna, including endemic species found nowhere else on earth. This biodiversity led to UNESCO recognizing Cuatrociénegas as an official biosphere reserve. There is, however, one place left where you can fully submerge yourself in these waters and take a swim: El Río Mezquites.

Unlike Poza Azul, which is a beautiful pool of blue hues, or las Playitas which is a vast lagoon, El Río Mezquites is a network of rivers. As you explore the twists and turns of El Río Mezquites, you might be accompanied by some curious turtles, also known as the Cuatrociénegas softshell (Apalone spinifera atra). They are a subspecies that can only be found in Cuatrociénegas. They have a snout that protrudes outwards like a pig as they wiggle back and forth thru the waters.

And if you are lucky, you might encounter Cuatrociénegas's iconic Coahuilan box turtle (Terrapene coahuila) as well, which is endemic to Cuatrociénegas. Unlike the soft-shell turtle, it is technically terrestrial. Due to the desert's harsh conditions, its ancestors started to explore the waters, and now they are only found on the land in the rainy season. However, this adaptation has left them with a predicament—they have no flippers between their toes, so they can't swim through the waters, but instead, they walk through shallow waters, reaching their long necks up to take a breath.

Only those animals and organisms, such as the box turtle, that are resilient enough and can adapt to the unique and harsh desert conditions can survive, which explains the high levels of endemism in the valley.

These unique species can be found on land and in the air, but to explore the endemism beneath, in the water, you’ll need to visit El Río Mezquites and remember to bring your snorkel so you can see them clearly in all their splendor.