This well designed tattoo is a black tortoise, which is is one of the Four Symbols of the Chinese constellations,  and it is often considered as a divine creature. It is sometimes called the Black Warrior of the North, and is known as Genbu in Japan, Hyeonmu in Korea and Huyền Vũ in Vietnam. In Taoist legend it was said that Xuánwǔ was the prince of a Chinese Emperor. However, he was not interested in taking the throne, but decided to study in Tao's way. At age 16, he left his parents to search for enlightenment in Tao's way. It was said that he eventually achieved god status and was worshipped as a god of northern sky.