According to legend, Ao was a large marine turtle

Turtle

Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...

 or tortoise

Tortoise

Tortoises are a family of land-dwelling reptiles of the order of turtles . Like their marine cousins, the sea turtles, tortoises are shielded from predators by a shell. The top part of the shell is the carapace, the underside is the plastron, and the two are connected by the bridge. The tortoise...

 who lived in the South China Sea

South China Sea

The South China Sea is a marginal sea that is part of the Pacific Ocean, encompassing an area from the Singapore and Malacca Straits to the Strait of Taiwan of around...

 during the time of the formation of the world by the goddess Nüwa

Nüwa

Nüwa is a goddess in ancient Chinese mythology best known for creating mankind and repairing the wall of heaven.-Primary sources:...

, creator of mankind. When Nüwa was repairing the sky she chopped off Ao’s four legs and used them as supports.

Another myth claims that Ao lived in the Bohai Sea

Bohai Sea

Bohai Sea , also known as Bohai Gulf, Bohai, or Bo Hai, is the innermost gulf of the Yellow Sea on the coast of Northeastern and North China. It is approximately 78,000 km2 Bohai Sea , also known as Bohai Gulf, Bohai, or Bo Hai, is the innermost gulf of the Yellow Sea on the coast of...

 and carried Mount Penglai (蓬莱山), Mount Fangzhang (方丈山) and Mount Yingzhou (瀛洲山) (three of the five Mountains of the Eight Immortals

Eight Immortals

The Eight Immortals are a group of legendary xian in Chinese mythology. Each Immortal's power can be transferred to a power tool that can give life or destroy evil. Together, these eight tools are called "Covert Eight Immortals" . Most of them are said to have been born in the Tang Dynasty or...

) on his back.