Cuero

In the cold Andean lakes of Patagonia and the river systems connecting them, the indigenous Mapuche people have maintained for centuries a profound wariness of the water. This wariness is embodied in the Cuero — a creature whose name means simply "cowhide" or "leather hide" — described as a large, flat, skin-like entity that floats on the surface of lakes, spreading itself wide and thin, and when an animal or person comes within reach, wrapping around its victim and pulling them beneath the surface to drown and consume them. The creature is reported from lakes in Argentina and Chile, with particular concentrations of accounts from the Lake Nahuel Huapi region and the Andean lacustrine belt.

Mapuche oral tradition is specific about the Cuero's behavior and appearance. The creature is described as roughly circular when spread flat, covered with eyes or claw-like projections around its edges that allow it to grip its prey, and capable of rapid movement when attacking. Some accounts describe it as resembling a giant ray or flatfish viewed from above, while others emphasize its mammalian quality — more like a stretched hide than a fish. The Cuero is said to be vulnerable to a particular thorny plant called the quinchamalí, whose branches, thrown onto the water's surface, cause the creature to retract and submerge, and which Mapuche travelers historically carried as a precaution when crossing Andean lakes.

Spanish colonial accounts from the seventeenth and eighteenth centuries documented the Cuero tradition among the Mapuche and neighboring peoples, noting the creature's feared status and the protective practices associated with crossing bodies of water. One particularly detailed account from a Jesuit missionary in the eighteenth century describes the creature as a genuine hazard to livestock crossing shallow lake margins. The consistency of the tradition across several centuries and the specificity of the protective plant remedy suggest a deep-rooted belief that predates the colonial period.

Cryptozoologists have proposed that the Cuero might represent a dramatically scaled-up version of a known animal — a giant freshwater stingray or skate is sometimes invoked, though no such animals are native to Andean lakes. Large populations of giant river otters once inhabited Patagonian waterways, and some researchers have suggested that a very large mustelid seen from above in murky water could produce a flattened, spreading silhouette. The cold, deep Andean lakes, some of which have not been fully surveyed, leave open at least a theoretical possibility of large, undescribed fauna.