Steller's sea ape

Recorded by Georg Wilhelm Steller during Vitus Bering's Great Northern Expedition on 10 August 1741 as an empirically observed but uncollected marine animal, which Steller provisionally named Simia marina. The account was published posthumously within the natural‑history literature rather than as a myth. Over subsequent centuries other naturalists assigned it to various marine mammal genera (e.g., Walbaum's Siren cynocephala; Shaw's Trichechus hydropithecus; Illiger's Manatus simia) and modern commentators generally treat it as either a misidentified northern fur seal or an unresolved cryptid due to the lack of a specimen.

Steller described an animal about 1.5–1.8 m long with a dog‑like head, pointed erect ears, large eyes, and long drooping whiskers likened to a Fu Manchu mustache. The body was elongated and robust, narrowing toward the tail, covered with thick fur gray dorsally and reddish‑white on the belly. Steller reported not observing forelimbs (later scholars suggest fore‑flippers may have been tucked). The tail had two fins, the upper fin larger than the lower, compared to a shark's tail. Steller also emphasized a human‑like upright posture when the creature raised about a third of its body out of the water.

Descriptions record animal behaviors rather than supernatural powers: sustained curiosity and playfulness (staring at the ship for around two hours), repeated swimming under and around the ship, rising partly out of the water in an upright posture for minutes, grasping a long seaweed stalk and manipulating or eating pieces of it. Steller attempted to shoot the animal but failed to secure a specimen. No supernatural abilities or powers are attributed in the sources.