The most disputed point in demarcating the border between China and Viet Nam is the Beibu Gulf, which is enclosed by the mainland of both countries and China’s Hainan Island. The gulf area covers a total of 128,000 square km. Until the 1970s, China and Viet Nam each administered the self-claimed territorial sea width. Yet as the two countries decided their own territorial waters, exclusive economic zones and continental shelf, they expanded these areas of administration. This inevitably led to a huge overlapping area of administration, which triggered constant quarrels. In December 2000, the two countries officially signed the Agreement on the Demarcation of the Beibu Gulf Territorial Waters, Exclusive Economic Zones and Continental Shelf in Beijing. According to the agreement the two countries get roughly the same size of marine area. The treaty also confirms the principle of jointly developing cross-border oil and natural gas resources, mineral resources and fishing resources. As a result, China withdrew a large number of fishing boats, transferring 150,000 fishery workers to other industries.