Terrifying footage captured the moment a massive fish chomped its jaws down on the head of a woman dressed as a mermaid as she performed underwater for children at a Chinese aquarium.

The fish bites down on Masha, 22, nearly fitting her whole head in its mouth while children and other spectators yell in horror.

Masha fights back and is able to free herself from the fish, which ripped off her goggles, before swimming quickly to the surface.

The performer suffered head, neck and eye injuries, according to Russian media reports, which published photos of her bruised and cut-up face.