According to local legend, when Vietnam had just started to develop into a country, they had to fight against invaders. To assist the Vietnamese in defending their country, the gods sent a family of dragons as protectors. This family of dragons began spitting out jewels and jade. These jewels turned into the islands and islets dotting the bay, linking together to form a great wall against the invaders. Under magics, numerous rock mountains abruptly appeared on the sea, ahead of invaders' ships; the forward ships struck the rocks and each other. After winning the battle, the dragons were interested in peaceful sightseeing of the Earth, and then decided to live in this bay. The place where the mother dragon descended was named Ha Long, the place where the dragon's children attended upon their mother was called Bai Tu Long island (Bai: attend upon, Tu: children, Long: dragon), and the place where the dragon's children wriggled their tails violently was called Bach Long Vy island (Bach: white-color of the foam made when Dragon's children wriggled, Long: dragon, Vy: tail), present day Tra Co peninsula, Mong Cai.