Is the Gulf of Tonkin international waters?

The Gulf of Tonkin is considered international waters, but it is adjacent to the territorial waters of Vietnam and China. Under international law, countries have sovereignty over waters extending 12 nautical miles from their Coastlines, while the remainder is classified as international waters. The Gulf of Tonkin has been a point of geopolitical tension, especially during the Vietnam War, but it remains largely open to navigation by all nations.