South China Sea

Hydrography

States and territories with borders on the sea (clockwise from north) include: the People's Republic of China, the Republic of China (Taiwan), the Philippines, Malaysia, Brunei, Indonesia, and Vietnam. Major rivers that flow into the South China Sea include the Pearl, Min, Jiulong, Red, Mekong, Menam, Rajang, Baram, Kapuas, Batang Hari, Musi, Kampar, Indragiri, Pahang, Agno, Pampanga, and Pasig Rivers.

The IHO in its Limits of Oceans and Seas, 3rd edition (1953), defines the limits of the South China Sea as follows:

On the South. The Eastern and Southern limits of Singapore and Malacca Straits [A line joining Tanjong Datok, the Southeast point of Johore (1°22′N 104°17′E / 1.367°N 104.283°E) through Horsburgh Reef to Pulo Koko, the Northeastern extreme of Bintan Island (1°13.5′N 104°35′E / 1.2250°N 104.583°E). The Northeastern coast of Sumatra] as far West as Tanjong Kedabu (1°06′N 102°58′E / 1.100°N 102.967°E) down the East coast of Sumatra to Lucipara Point (3°14′S 106°05′E / 3.233°S 106.083°E) thence to Tanjong Nanka, the Southwest extremity of Banka Island (where it transitions as Java Sea), through this island to Tanjong Berikat the Eastern point (2°34′S 106°51′E / 2.567°S 106.850°E), on to Tanjong Djemang (2°36′S 107°37′E / 2.600°S 107.617°E) in Billiton, along the North coast of this island to Tanjong Boeroeng Mandi (2°46′S 108°16′E / 2.767°S 108.267°E) and thence a line to Tanjong Sambar (3°00′S 110°19′E / 3.000°S 110.317°E) the Southwest extreme of Borneo.

On the East. From Tanjong Sambar through the West coast of Borneo to Tanjong Sampanmangio, the North point, thence a line to West points of Balabac and Secam Reefs, on to the West point of Bancalan Island and to Cape Buliluyan, the Southwest point of Palawan, through this island to Cabuli Point, the Northern point thereof, thence to the Northwest point of Busuanga and to Cape Calavite in the island of Mindoro, to the Northwest point of Lubang Island and to Point Fuego (14°08'N) in Luzon Island, through this island to Cape Engano, the Northeast point of Luzon, along a line joining this cape with the East point of Balintang Island (20°N) and to the East point of Y'Ami Island (21°05'N) thence to Garan Bi, the Southern point of Taiwan (Formosa), through this island to Santyo (25°N) its North Eastern Point.

On the North. From Fuki Kaku, the northern point of Formosa, to Kiushan Tao (Turnabout Island), on to the southern point of Haitan Tao (25°25'N) and thence westward on the parallel of 25°24' North to the coast of Fukien.

On the West. The Mainland, the Southern limit of the Gulf of Thailand, and the East coast of the Malay Peninsula.

However, in a revised draft edition of Limits of Oceans and Seas, 4th edition (1986), the International Hydrographic Organization recognized the Natuna Sea. Thus, the southern limit of the South China Sea would be revised from the Bangka Belitung Islands to the Natuna Islands.

The South China Sea has an average depth of 1,212 m (3,976 ft), and the deepest recorded point is either 5,559 m (18,238 ft) or 5,567 m (18,264 ft).

Geology

The sea lies above a drowned continental shelf; during recent ice ages, global sea level was hundreds of metres lower, and Borneo was part of the Asian mainland.

The South China Sea opened around 45 million years ago when the "Dangerous Ground" rifted away from southern China. Extension culminated in seafloor spreading around 30 million years ago, a process that propagated to the southwest, resulting in the V-shaped basin we see today. Extension ceased around 17 million years ago.

Arguments have continued about the role of tectonic extrusion in forming the basin. Paul Tapponnier and colleagues have argued that as India collides with Asia, it pushes Indochina to the southeast. The relative shear between Indochina and China caused the South China Sea to open. This view is disputed by geologists who do not consider Indochina to have moved far relative to mainland Asia. Marine geophysical studies in the Gulf of Tonkin by Peter Clift have shown that the Red River Fault was active and causing basin formation at least by 37 million years ago in the northwest South China Sea, consistent with extrusion playing a part in the formation of the sea. Since opening, the South China Sea has been the repository of large sediment volumes delivered by the Mekong River, Red River, and Pearl River. Several of these deltas are rich in oil and gas deposits.

Islands and seamounts

The South China Sea contains over 250 small islands, atolls, cays, shoals, reefs, and sandbars, most of which have no indigenous people, many of which are naturally underwater at high tide, and some of which are permanently submerged. The features are:

• The Spratly Islands
• The Paracel Islands
• Pratas Island and the Vereker Banks
• The Macclesfield Bank
• The Scarborough Shoal

The Spratly Islands span an area of approximately 810 by 900 km, covering around 175 identified insular features, the largest being Taiping Island (Itu Aba) at just over 1.3 kilometres (0.81 mi) long and with its highest elevation at 3.8 metres (12 ft).

The largest singular feature in the area of the Spratly Islands is a 100 kilometres (62 mi) wide seamount called Reed Tablemount, also known as Reed Bank, in the northeast of the group, separated from Palawan Island of the Philippines by the Palawan Trench. Now completely submerged, with a depth of 20 metres (66 ft), it was an island until it was covered approximately 7,000 years ago by increasing sea levels after the last ice age. With an area of 8,866 square kilometres (3,423 sq mi), it is one of the largest submerged atoll structures in the world.

Trade route

The South China Sea has historically been an important trade route between northeast Asia, China, southeast Asia, and going to India and the West. The number of shipwrecks of trading ships that lie on the ocean's floor attests to a thriving trade going back centuries. Nine historic trade ships carrying ceramics dating back to the 10th century until the 19th century were excavated under Swedish engineer Sten Sjöstrand.

Of the world's $16 trillion maritime shipping, $3.4 trillion passed through the South China Sea in 2016. The 2019 data showed that the sea carries trade equivalent to 5 percent of global GDP.

In 2023, the South China Sea remained a major energy trade route, with 10 billion barrels of petroleum and petroleum products and 6.7 trillion cubic feet of liquefied natural gas passing through it. The LNG volume represented 34% of global LNG trade.

Natural resources

In 2012–2013, the United States Energy Information Administration estimated that there is relatively little oil and natural gas in contested areas such as the Paracel and the Spratly Islands. Most of the proved or probable 11 billion barrels of oil and 190 trillion cubic feet of natural gas in the South China Sea exist near undisputed shorelines.

In 2010, the Western Central Pacific (excluding the northernmost reaches of the South China Sea closest to the PRC coast) accounted for 14% of the total world catch from commercial fishing of 11.7 million tonnes. This was up from less than 4 million tonnes in 1970.

China announced in May 2017 a breakthrough for mining methane clathrates, when they extracted methane from hydrates in the South China Sea, but commercial adoption may take a decade or more.

Territorial claims

Several countries have made competing territorial claims over the South China Sea. Such disputes have been regarded as some of Asia's potentially most dangerous points of conflict. Both the People's Republic of China (PRC) and the Republic of China (ROC, commonly known as Taiwan) claim almost the entire body as their own, demarcating their claims within what is known as the "nine-dash line", which claims overlap with virtually every other country in the region. Competing claims include:

• Indonesia, Vietnam, China, and Taiwan over the waters northeast of the Natuna Islands
• The Philippines, China, and Taiwan over Scarborough Shoal.
• Vietnam, China, and Taiwan over the waters west of the Spratly Islands. Some or all of the islands themselves are also disputed between Vietnam, China, Taiwan, Brunei, Malaysia, and the Philippines.
• The Paracel Islands are disputed between China, Taiwan, and Vietnam.
• Malaysia, Cambodia, Thailand, and Vietnam over areas in the Gulf of Thailand.
• Singapore and Malaysia along the Strait of Johore and the Strait of Singapore.

China and Vietnam have both been vigorous in prosecuting their claims. China (various governments) and South Vietnam each controlled part of the Paracel Islands before 1974. A brief conflict in 1974 resulted in 18 Chinese and 53 Vietnamese deaths, and China has controlled the whole of the Paracel since then. The Spratly Islands have been the site of a naval clash, in which over 70 Vietnamese sailors were killed just south of Chigua Reef in March 1988. Disputing claimants regularly report clashes between naval vessels, and these now also include airspace incidents.

ASEAN, in general, and Malaysia, in particular, have been keen to ensure that the territorial disputes within the South China Sea do not escalate into armed conflict. As such, joint development authorities have been established in areas of overlapping claims to jointly develop the area and divide the profits equally without settling the issue of sovereignty over the area. This is true particularly in the Gulf of Thailand. Generally, China has preferred to resolve competing claims bilaterally, while some ASEAN countries prefer multilateral talks, believing that they are disadvantaged in bilateral negotiations with the much larger China and that, because many countries claim the same territory, only multilateral talks could effectively resolve the competing claims.

The overlapping claims over Pedra Branca or Pulau Batu Putih, including the neighbouring Middle Rocks, by both Singapore and Malaysia were settled in 2008 by the International Court of Justice, awarding Pedra Branca/Pulau Batu Puteh to Singapore and the Middle Rocks to Malaysia. In July 2010, US Secretary of State Hillary Clinton called for China to resolve the territorial dispute. China responded by demanding that the US keep out of the issue. This came at a time when both countries had been engaging in naval exercises as a show of force to the opposing side, which increased tensions in the region. The US Department of Defense released a statement on August 18 where it opposed the use of force to resolve the dispute, and accused China of assertive behaviour. On July 22, 2011, one of India's amphibious assault vessels, the INS Airavat which was on a friendly visit to Vietnam, was reportedly contacted at a distance of 45 nautical miles (83 km) from the Vietnamese coast in the disputed South China Sea on an open radio channel by a vessel identifying itself as the Chinese Navy and stating that the ship was entering Chinese waters. The spokesperson for the Indian Navy clarified that, as no ship or aircraft was visible from INS Airavat, it proceeded as scheduled on its onward journey. The Indian Navy further clarified that "[t]here was no confrontation involving the INS Airavat. India supports freedom of navigation in international waters, including in the South China Sea, and the right of passage in accordance with accepted principles of international law. These principles should be respected by all."

In September 2011, shortly after China and Vietnam had signed an agreement seeking to contain a dispute over the South China Sea, India's state-run explorer, Oil and Natural Gas Corporation (ONGC) said that its overseas investment arm ONGC Videsh Limited had signed a three-year deal with Petrovietnam for developing long-term cooperation in the oil sector and that it had accepted Vietnam's offer of exploration in certain specified blocks in the South China Sea. In response, Chinese Foreign Ministry spokesperson Jiang Yu issued a protest. The spokesman of the Ministry of External Affairs of the Government of India responded by saying that "The Chinese had concerns, but we are going by what the Vietnamese authorities have told us and have conveyed this to the Chinese." The Indo-Vietnamese deal was also denounced by the Chinese state-run newspaper Global Times.

In 1999, Taiwan claimed the entirety of the South China Sea islands under the administration of Lee Teng-hui. The entire subsoil, seabed, and waters of the Paracels and Spratlys are claimed by Taiwan.

In 2012 and 2013, Vietnam and Taiwan butted heads against each other over anti-Vietnamese military exercises by Taiwan.

In May 2014, China established an oil rig near the Paracel Islands, leading to multiple incidents between Vietnamese and Chinese ships. Vietnamese analysis identifies this change in strategy, generating ongoing incidents as occurring since 2012.

In December 2018, retired Chinese admiral Luo Yuan proposed that a possible solution to tensions with the United States in the South China Sea would be to sink one or two United States Navy aircraft carriers to break US morale. Also in December 2018, Chinese commentator and Senior Colonel in the People's Liberation Army Air Force, Dai Xu, suggested that China's navy should ram United States Navy ships sailing in the South China Sea.

The US, although not a signatory to UNCLOS, has maintained its position that its naval vessels have consistently sailed unhindered through the South China Sea and will continue to do so. At times, US warships have come within the 12 nautical-mile limit of Chinese-controlled islands (such as the Paracel Islands), arousing China's ire. During the US Chief of Naval Operations' visit to China in early 2019, he and his Chinese counterpart worked out rules of engagement, whenever American warships and Chinese warships encounter on the high seas.

On 26 June 2020, the 36th Association of Southeast Asian Nations (ASEAN) Summit was held virtually. Vietnam, as the Chairman of the Summit, released the Chairman's Statement. The statement said the United Nations Convention on the Law of the Sea is "the basis for determining maritime entitlements, sovereign rights, jurisdiction and legitimate interests over maritime zones, and the 1982 UNCLOS sets out the legal framework within which all activities in the oceans and seas must be carried out."

In November 2025, Australia raised concerns over China's military expansion in the South and East China Seas, citing increased risks to trade routes. The remarks followed an incident in which a Chinese fighter jet dropped flares near an Australian patrol plane, deemed “unsafe and unprofessional,” and were made during the Indo-Pacific Navy Conference amid Australia's AUKUS nuclear submarine program.

2016 arbitration

In January 2013, the Philippines initiated arbitration proceedings against China (PRC) over issues surrounding the nine-dash line, characterization of maritime features, and EEZ. China did not participate in the arbitration.

On 12 July 2016, an arbitral tribunal ruled in favor of the Philippines on most of its submissions. It clarified that it would not "rule on any question of sovereignty over land territory and would not delimit any maritime boundary between the Parties" but concluded that China had not historically exercised exclusive control within the nine-dash line, hence has "no legal basis" to claim "historic rights" over the resources. It also concluded that China's historic rights claims over the maritime areas (as opposed to land masses and territorial waters) inside the nine-dash line would have no lawful effect outside of what is entitled to under UNCLOS. It criticized China's land reclamation projects and its construction of artificial islands in the Spratly Islands, stating that it had caused "severe harm to the coral reef environment." Finally, it characterized Taiping Island and other features of the Spratly Islands as "rocks" under UNCLOS, and therefore are not entitled to a 200 nautical mile exclusive economic zone. The arbitral tribunal decision was ruled as final and non-appealable by either country.

China rejected the ruling, calling it "ill-founded". China's response was to ignore the arbitration result and to continue pursuing bilateral discussions with the Philippines.

Taiwan, which currently administers Taiping Island, the largest of the Spratly Islands, also rejected the ruling. As of November 2023, 26 governments support the ruling, 17 issued generally positive statements noting the ruling but not calling for compliance, and eight rejected it. The governments in support are Australia, Austria, Belgium, Canada, the Czech Republic, Denmark, Finland, France, Germany, Greece, India, Ireland, Italy, Japan, the Netherlands, New Zealand, the Philippines, Poland, Portugal, Romania, Slovakia, South Korea, Spain, Sweden, the United Kingdom, and the United States; the governments in opposition are China, Montenegro, Pakistan, Russia, Sudan, Syria, Taiwan, and Vanuatu. The United Nations itself does not have a position on the legal and procedural merits of the case or on the disputed claims, and the Secretary-General expressed his hope that the continued consultations on a Code of Conduct between ASEAN and China under the framework of the Declaration of the Conduct of Parties in the South China Sea will lead to increased mutual understanding among all the parties.