China maps the ocean floor to prepare for a submarine war with the U.S.

China has been conducting an extensive undersea mapping operation and monitoring across the Pacific Ocean, Indian Ocean and Arctic Oceans. This vast operation is aimed at gaining detailed knowledge about marine conditions, which naval experts believe will be vital for the conduct of submarine warfare against America and its allies.

Ship-tracking data shows that, for example, in 2024 and 2025, the Dong Fang Hong 3?a research ship operated by Ocean University of China sailed back and forth between the seas around Taiwan, Guam and strategic stretches of Indian Ocean. Ocean University reports that in October 2024 it tested a series of powerful Chinese ocean sensors able to identify undersea items near Japan. It returned to the same area last May. In March 2025 it covered the approaches to the Malacca Strait - a crucial chokepoint for maritime trade - by crisscrossing the waters between Sri Lanka, Indonesia and the Malacca Strait.

According to the university the ship carried out climate research and mud surveys. A scientific paper written by Ocean University academics reveals that the ship has also carried out extensive deep-sea maps. According to U.S. Navy officials and naval-warfare specialists, the Dong Fang Hong 3's deep-sea mapping and sensor placement gives China an idea of what conditions are under the sea so it can better deploy its subs and track down its enemies.

The Dong Fang Hong 3 doesn't operate alone. The Dong Fang Hong 3 is part of an ocean mapping and monitoring effort involving hundreds of sensors and dozens of research ships. This effort was traced by examining Chinese government records and university publications, as well as journal articles and scientific papers, and analyzing more than five years' worth of movement data from 42 research vessels operating in the Pacific Ocean, Indian Ocean, or Arctic Ocean using a ship tracking platform developed by New Zealand-based Starboard Maritime Intelligence.

Nine naval warfare experts who reviewed the findings said that while the research is primarily civilian - for example, some areas are being surveyed to determine fishing grounds and mineral deposits - there are also military purposes.

In order to gather information on the underwater terrain, researchers map the seafloor by traveling in tight lines. This type of movement is shown in the tracking data of vessels that have been tracked over large areas of the Pacific Ocean, Indian Ocean and Arctic Ocean.

According to an analysis of Chinese state-run media, descriptions of vessels published by Chinese universities and press releases from government organizations, at least eight of those tracked vessels have performed seabed mapping. Another 10 of them have carried mapping equipment.

Peter Scott, former chief of Australia’s submarine force, stated that the survey data from the vessels "would potentially be invaluable in preparing for the battlespace" of Chinese submarines. "Any submariner who is worth his salt will spend a lot of time and effort to understand the environment in which he operates."

Ship-tracking data shows that China's seabed surveying effort is concentrated in part around militarily-important waters near Guam, Hawaii, the Philippines and China. Wake atoll is a military base in the north Pacific.

Jennifer Parker, adjunct professor of Defense and Security at the University of Western Australia (and former Australian antisubmarine warfare officers), said that "the scale of their actions is more than just about resources." If you take a look at its sheer size, it is clear that the Australians intend to build a blue-water navy that includes submarine operations.

Parker and other experts also added that, even when data are gathered for scientific reasons, the integration between civilian scientific research, and military?technology has become a major focus of the Chinese Government under President Xi Jinping. Beijing calls this "civil-military" fusion.

The Chinese ministries of foreign affairs, defense and natural resources did not respond to inquiries about ocean monitoring and seabed mapping.

The U.S. Defense Department did not respond to any questions.

Rear Admiral Mike Brookes of the U.S. Office of Naval Intelligence testified to a congressional committee this month that China has dramatically increased its surveying activities, providing data "that enable submarine navigation, concealment and positioning of seabed weapons or sensors." Brookes also said that the "potential collection of military intelligence" by Chinese research vessels "represents an important strategic concern." The United States has recently reorganized its efforts to map the ocean and monitor it, but they do so using military vessels which are permitted to disable the civilian tracking software. China's civilian survey vessels also disable tracking at times, so its campaign could go further than we can determine. It is the first report on the extent of China’s mapping and monitoring efforts across the Pacific Ocean, Indian Ocean and Arctic Ocean. In previous reporting, a small portion of China's mapping and monitoring effort was revealed around Guam and Taiwan and in some parts of the Indian Ocean.

Ryan Martinson, a U.S. associate professor who specializes in Chinese maritime strategies, said: "It's truly astonishing to see the immense scale of Chinese marine science research." Naval War College.

Martinson added, "For decades the U.S. Navy was able to assume an asymmetrical advantage due to its knowledge of ocean battlespace." China's efforts "threaten that advantage." This is obviously very concerning.

"PARANOID about being boxed in"

According to naval experts, the data collected by Chinese research vessels about seabeds and water conditions are crucial for submarine operations and antisubmarine warfare. According to Australian defense scholar Parker: Commanders need information about the underwater terrain in order to avoid collisions, and conceal their vessels.

This data is essential to detect submarines that operate within a few hundred metres of the surface. Submarines can be identified by the sound they make or echoes of signals from sonar systems. Tom Shugart is a former U.S. sub commander and adjunct senior fellow with the Center for a New American Security. He said that the sound waves move differently depending on the underwater terrain.

Water temperature, salinity, and currents also affect sound waves and submerged movements.

The vessels in question belong to Chinese state entities such as the Ministry of Natural Resources, or to state-affiliated institutions of higher learning like Ocean University. In 2021, its president publicly celebrated "close ties with China's Navy" and "commitment to building a maritime force and national defense." The university did not respond to a comment request.

China's most extensive ocean surveying has been done east of the Philippines. The Philippines is located along the First Island Chain. This chain of territories, largely controlled and governed by America, runs from the Japanese Islands in the north, through Taiwan, to Borneo, in the south. The chain is a natural barrier that separates China's coast seas from the Pacific.

Peter Leavy, former Australian naval attache in the U.S. who is now the president of the Australian Naval Institute, said that the First Island Chain was a source of paranoia for the Australians. China's mapping is "an indication of a desire to better understand the maritime domain in order to break out."

China's tracking data also shows that it covers the waters around Guam, where American nuclear submarines have been stationed.

Chinese vessels also mapped the waters surrounding Hawaii, another of America's regional military hubs. They examined an underwater ridge to the north of a base in Papua New Guinea, where the U.S. gained access recently. And they scouted Christmas Island, a territory of Australia on a route connecting the South China Sea with a crucial Australian submarine base. China's efforts go beyond the South China Sea. China has also mapped vast?swathes of the Indian Ocean. This is a crucial route for Chinese imports from the Middle East, Africa and the Middle East.

Parker, a former anti-submarine war officer, said that China has "some key vulnerabilities" when it comes its dependence on maritime trade. Surveying indicates that "they will likely conduct more submarine operations in Indian Ocean".

China's ships have also mapped seabeds west and north from Alaska, a vital sea route to the Arctic. Beijing has declared the Arctic a strategic frontier, and its ambition is to become a great polar power by 2030.

Shugart said that the extensive surveying, and Beijing's increasing undersea capabilities are "symptomatic" of China's rising as a leading maritime power.

A 'TRANSSPARENT OCEAN'

Wu Lixin proposed an ambitious project to create a transparent ocean in 2014 by deploying sensors to give China a complete view of the water conditions and its movement. This was according to a report published by the Chinese Academy of Sciences, which is affiliated with state. According to Shandong officials, the Shandong government quickly backed this proposal with at least $85 millions.

Ocean University has announced that it began the project in the South China Sea where they have built an observation system covering the deep-sea area.

Brookes Brookes, director of the U.S. Office of Naval Intelligence told the Congressional?commission China was building underwater surveillance networks to "gather hydrographic information - water temperatures, salinity and currents – in order to optimize sonar performances and enable persistent surveillance of subs transiting crucial waterways such as the South China Sea."

Chinese scientists have expanded the project transparent ocean to include the Pacific and Indian Oceans after surveying the South China Sea. Records from the Chinese Ministry of Natural Resources and Shandong Government show that China deployed hundreds of sensors and buoys in the Pacific to detect changes like temperature and salinity.

Documents from the Ministry of Natural Resources and the Chinese Academy of Sciences describe an array of sensors ringing India, Sri Lanka and the Ninety East Ridge, a mountain range under the Indian Ocean. Starboard data shows that Chinese vessels also explored the ridge, which is one of the longest underwater mountain ranges in the world. It sits on the approach to Malacca Strait - through which a large part of China's oil supplies passes.

Ocean University and Institute of Oceanology of the Chinese Academy of Sciences have stated that the larger network of sensors provides China with data in real time about the water conditions and movements of subsea.

Experts in naval warfare cautioned against this claim due to the technical difficulties of real-time data transmission from under water. Parker stated that even delayed data could be valuable as it can help China detect U.S. sub operations. Many sensors are located in sensitive areas. Recently, the media reported that the U.S. was fortifying a crucial strait connecting Taiwan and the Philippines in order to block Chinese access to Pacific. Ocean University reports that China has installed?advanced sensor systems in areas of the strait where U.S. subs could move through to reach the South China Sea.

Chinese scientists claim that these sensors monitor changes in ocean and climate conditions. In 2017, Shandong officials said that the transparent ocean project aimed to "ensure maritime security and defense" and compared it with the U.S. military's effort?to create an American ocean sensor network.

The Chinese Academy of Sciences, Shandong Government and Institute of Oceanology did not respond to comments.

According to the website of the Naval Submarine Academy in China, the founder of the Mapping-Program, Wu, now oversees the Network through the Qingdao National Laboratory for Marine Science and Technology. Wu did not respond to any questions.

'NEW TYPES OF COMBAT CAPABILITIES'

China's mapping system and monitoring tools give it the sophisticated tools needed to detect and destroy rival submarines in some of world's most volatile waters.

Collin Koh is a senior fellow at Singapore's RSIS Institute of Defence and Strategic Studies. He said that this was a manifestation of China’s vast sea reach. "They have a fairly good idea of the maritime domain that they want to operate in either in peacetime, or during war."

Chinese researchers also see the strategic value of their work. Zhou Chun is a researcher at Ocean University who supervises the Indian Ocean sensor arrays and Pacific Ocean sensor arrays. He was quoted in a press release from Ocean University last year as saying that he had seen "the rapid growth of my country's military and maritime capabilities." He did not respond to any questions.

Zhou promised to "transform our military's most advanced technological and scientific achievements into new combat capabilities at sea."

(source: Reuters)