Nahuelito is a serpentine monster supposedly native to Nahuel Huapi Lake, near Bariloche city, in the Province of Río Negro, Patagonia, Argentina.

Nahuelito is named after the lake it supposedly inhabits.

The legend of Nahuelito reportedly originated among aboriginal tribes, such as the Mapuche. The Mapuche told the first European settlers stories about a monster in the Nahuel Huapi.

Nahuel Huapi is not the only Patagonian lake with an alleged serpentine monster. There have also been monster sightings in other lakes across the Patagonian region.

Aboriginal communities say that a cow-like monster lives in Patagonian Lago Lácar.


Descriptions of Nahuelito rely on alleged photographic evidence and alleged eyewitness accounts.

Nahuelito is similar to the Loch Ness monster. It is supposedly a humped serpentine monster. However, the legend of Nahuelito predates the Lochness Monster because it was part of the centuries-old legends of the Mapuche aboriginals before European settlers arrived.

Some cryptozoologists believe that Nahuelito, like the Lochness Monster, is possibly a surviving plesiosaur.

Plesiosaurs are an ancient order of aquatic reptiles believed extinct.

George Garrett, who investigated reports about Nahuelito, described it as a snake-like creature. He saw it rising about 6 feet above the water and estimated the visible section of the monster was about 15-20 feet long.

Other alleged eyewitnesses estimated the creature was about 15-150 feet long.

Sightings and Tales

Although the legend of Nahuelito predated the arrival of European settlers, it wasn’t until the late 19th century that the alleged lake monster started drawing widespread attention.

Clemente Onelli’s Buenos Aires Zoo expeditions

Patagonia is a region of Argentina with many lakes.

Reports about lake monsters originating from multiple Patagonian communities started circulating widely in the late 19th century. The stories came to the attention of Clemente Onelli, the director at the Buenos Aires Zoo.

Onelli probably first heard about strange animals in the region in 1897 when a local farmer told him about mysterious noises at night and sightings of a long-necked reptilian monster on the shores of Patagonia’s White Lake.

Various descriptions of the lake monsters suggested to Onelli that plesiosaur-like monsters lived in lakes across Patagonia, including Nahuel Huapi Lake.

Under Onelli’s direction in March 1922, the Buenos Aires Zoo began investigating the allegations of plesiosaur-like monsters in the Nahuel Huapi Lake lake and neighboring lakes in the Patagonian region.

Besides the Nahuel Huapi Lake, the zoo also investigated reported sightings from regional lakes such as Lago Lácar and the Laguna del Plesiosaurio or Plesiosaur Lake (formerly Laguna Negra or Black Lagoon).

The Martin Sheffield letter

In January 1922, Onelli received a letter from the Texan gold prospector and adventurer Martin Sheffield (c.1863-1932) alleging a monster at Laguna Negra. Sheffield’s letter was probably the report that finally spurred Onelli to equip an expedition led by José Cihagi to investigate the claimed sightings at various Patagonian lakes.

According to Sheffield, the Laguna Negra monster was “an animal with a head like a swan and enormous size. The movement in the water makes me suppose a crocodile body.”

Some believe that Sheffield’s description of the Laguna Negra monster might have been influenced by Arthur Conan Doyle’s The Lost World (1912), in which a character described a lake monster that was “like a huge swan, with clumsy body and a highly flexible neck.”

The Buenos Aires Zoo expedition found no evidence supporting the widespread allegations.

George Garrett’s Toronto Globe report

George Garrett, one of the early investigators of the monster reports, claimed a sighting of the Nahuelito in 1910.

He shared the details of his alleged encounter with the Nahuelito with the Toronto Globe in 1922. According to the report, Garrett saw the creature rising about 6.6 feet above the water at a distance of about 400 meters.

He said the section of the monster’s body revealed when it rose above the water was 15- 20 feet long.

Garrett said that he shared his experience with people in neighboring communities. They likewise regaled him with tales about past sightings.

Garrett organized an expedition to find the Nahuelito

Following the sighting in 1910, Garret organized an expedition to search for the Nahuelito. The 1922 expedition, sponsored by the Buenos Aires Zoo’s Clemente Onelli, also found no evidence of a monster in the Nahuel Huapi Lake.

The Argentine Navy incident

After the failed expedition by the Buenos Aires Zoo in the early 20th century, interest in the Nahuelito and its monster cousins revived again in the 1960s following a report that an Argentine Naval ship detected a mysterious presence in the Nahuel Huapi Lake.

Naval officials allegedly tracked the mysterious body in the water for nearly three weeks but could not determine its nature.

Many cryptozoologists believed that the incident provided new evidence that a mysterious monster inhabited the lake.

Multiple media reports in the 1980s also revived interest in the Patagonian monsters. Newspapers also carried stories about alleged sightings of a mysterious creature in the Nahuel Huapi Lake.

Alleged photographic evidence of Nahuelito

Argentine newspapers published the first alleged photos of the Nahuelito in 1988. But the image was blurry, and many people believed they were hoaxes.

In 2006, another Argentine newspaper published a photograph purportedly showing Nahuelito. But like the 1988 photo, it is widely suspected to be a hoax.

Nahuelito has been the subject of many TV shows. Cryptozoologist Josh Gates investigated claimed sightings of the lake monster on SyFy’s Channel’s Destination Truth.

What is Nahuelito?

The plesiosaur theory

The plesiosaur theory is perhaps the most favored cryptozoological theory of the Nahuelito and similar lake monsters, such as the Loch Ness Monster and Morag.

Plesiosaurs (order Plesiosauria) are extinct aquatic reptiles that lived in the Mesozoic era (250-65 million years ago).

They first appeared in the latest Triassic Period (c. 250-200 million years ago) and flourished during the Jurassic Period (200–145.0 million years). Plesiosaurs went extinct toward the end of the Cretaceous (145-65 million years).

Plesiosaurus (Plesiosaurus dolichodeirus) is the best-known genus of the order Plesiosauria.

The reptiles were aquatic creatures with elongated bodies, long necks, small heads, and flippers.

Plesiosaurus is the favorite cryptozoological candidate for lake monsters such as Nahuelito, Loch Ness Monster, and Morag because the physical features of the ancient species match descriptions of the lake cryptids.

The mutant theory

A second popular theory about Nahuelito proposes that it was a mutant created by experiments conducted on Huemul Island during the 1950s.

Huemel is an island in the Nahuel Huapi Lake, off the shore of San Carlos de Bariloche city in the Province of Río Negro, Argentina.

Scientists researched on the island to develop a fusion power device known as the Thermotron.

The submarine theory

The February 1960 Argentine Navy incident inspired the theory that Nahuelito might be an underwater craft or vessel.

Some locals believe that Nahuelito could be a space alien submarine craft.

Other Name/s
TypeLake Monster

References, “The Plesiosaur at Laguna Negra,” accessed on March 5, 2023., “The Nahuelito enigma,” accessed on March 5, 2023., “In Pursuit of the Patagonian Plesiosaur,” accessed on March 5, 2023., “Andean ‘Plesiosaurus’ May Be an Armadillo Or Modern Megatherium, Onelli Thinks,” The New York Times, (1922), accessed on March 5, 2023., “Did ‘Nahuelito’ reappear?” translated from Spanish and accessed on March 5, 2023., “Nessie and Other Lake Monsters,” by Mark Chorvinsky, accessed on March 5, 2023.

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