- Country reported: Mexico
The ahuízotl is described as a dog-like animal with a smooth black coat, humanoid hands, a bony spur beneath its tail, and a tail tip which also resembles a human hand. It is described in the Florentine Codex:
- "...very like the teui, the small teui dog; small and smooth, shiny. It has small, pointed ears, just like a small dog. It is black, like rubber; smooth, slippery, very smooth, long-tailed. And its tail is provided with a hand at the end; just like a human hand is the point of its tail. And its hands are like a raccoon's hands or like a monkey's hands. It lives, it is a dweller in watery caverns, in watery depths. And if anyone arrives there at its entrance, or there in the water where it is, it then grabs him there. It is said that it sinks him, it plunges him into the water; it carries him to its home, it introduces him to the depths; so its tail goes holding him, so it goes seizing him ... [When the body is retrieved] the one it has drowned no longer has his eyes, his teeth, and his nails; it has taken them all from him. But his body is completely unblemished, his skin uninjured. Only his body comes out all slippery-wet; as if one had pounded it with a stone; as if it had inflicted small bruises ... When it was annoyed - had caught no one, had drowned none of us commoners - then was heard as if a small child wept. And he who heard it thought perhaps a child wept, perhaps a baby, perhaps an abandoned one. Moved by this, he went there to look for it. So there he fell into the hands of the auítzotl, there it drowned him..."
The ahuizotl is commonly supposed to have had spines or spiky hair on its body, which has been explained by some cryptozoologists as wet hair clumped into spikes. However, these spines are based on a misinterpretation of the Aztec depiction of water, and there are a number of Aztec images of the ahuizotl as a smooth-furred animal.
Ferdinand Anders suggested it may have been the coyote, which, however, do not like water. The Mexican hairy porcupine was suggested by Eduard Seler, but that animal is arboreal and not aquatic. Some form of otter is the most common explanation: either the marine otter, sea otter, or neotropical otter. Andrew Gable also suggested an unknown species of prehensile-tailed otter, and Matthew McDavitt suggests it was a stylized depiction of the yapock.
- The California water-dog, a predatory otter-like animal of Native American folklore
- The pavawkyaiva, an otter-like "water dog" of Arizona and New Mexico
- Water tigers, aquatic predators of South America