Shui-mu Niang-niang was a Chinese water demon whose evil doings caused yearly floods, claiming numerous lives and bringing famine and desolation to the town of Ssu Chou and its surroundings.
Her power was so great that her cunning tricks triumphed over the troops Yo Huang, the Lord of the Skies, had sent out against her.
The demoness, enraged by the repeated attempts to capture her, kicked and turned over one of the magic buckets containing the sources of the great lakes. The freed water engulfed the unfortunate town of Ssu Chou, burying it for ever under a great mass of water called the lake of Hung-tse.
Now Yo Huang’s patience was exhausted, and he methodically organized her capture. Great heroes and large armies pursued her relentlessly. One day, having narrowly escaped after a furious race, Shui-mu stopped utterly exhausted and famished. She caught sight of an old hag selling bowls of freshly cooked noodles. Avidly she began to devour the food, unaware that she had fallen into a trap. The old woman was Kuan-yin Pusa, a good woman with great magical powers.
In Shui-mu’s stomach the noodles turned into iron chains, winding around her entrails. The chain's end, protruding from her mouth, welded itself to the noodles-turned-chains remaining in the dish. Bound and powerless, the demon was led away to be fastened securely at the bottom of a deep well, where she was to remain a prisoner for all times. The people of that province say that the end of the chain can be seen whenever the water level in the well drops particularly low.