SYDNEY, March 24 - China is carrying out a sweeping program of undersea surveying and ocean monitoring that reaches across the Pacific, Indian and Arctic oceans, assembling a detailed picture of seabed topography and water conditions. Naval analysts say that information is precisely the kind of data maritime forces need to plan and conduct submarine operations and to detect opposing submarines.
One of the vessels active in this campaign, the Dong Fang Hong 3, operated by Ocean University of China, sailed repeatedly during 2024 and 2025 through waters adjacent to Taiwan and near Guam, and traversed key stretches of the Indian Ocean, according to ship movement records. In October 2024, the vessel inspected a set of powerful Chinese ocean sensors near Japan, and revisited the same area in May. In March 2025 it carried out repeated crossings of the waters between Sri Lanka and Indonesia, mapping approaches to the Malacca Strait - a narrow passage that is a critical chokepoint for maritime commerce.
Ocean University has described the Dong Fang Hong 3’s missions as involving mud surveys and climate research. At the same time, a scientific paper co-authored by academics at the university documents extensive deep-sea mapping conducted by the ship. Naval experts and U.S. officials view these activities as providing detailed hydrographic and acoustic data that are directly relevant to planning and executing submarine operations in contested waters.
The Dong Fang Hong 3 is part of a far broader program of mapping and monitoring that involves scores of research ships and a network of sensors. An analysis of more than five years of vessel movements for 42 research ships active in the Pacific, Indian and Arctic oceans, together with reviews of Chinese government and university records and scientific literature, indicates a coordinated set of missions by state or state-affiliated entities. These operations include seabed mapping, deployment of sensor arrays and placement of buoys and subsea equipment.
While the publicly stated purposes for much of the activity are civilian - such as mapping fishing grounds or conducting mineral prospecting in areas where China holds contracts - nine naval-warfare experts who reviewed the available material said the same data would be valuable for military planning. The kind of information gathered by research vessels - repeated, tight-line transects across a survey area that reveal the contours and features of the ocean floor - is visible in ship-tracking records for many of the vessels involved.
At least eight of the tracked ships have carried out direct seabed mapping missions, and another 10 have been fitted with equipment commonly used for mapping, according to an examination of state media reports, vessel descriptions published by Chinese academic institutions and government press materials. The survey patterns recorded in vessel movement logs - frequent back-and-forth runs over a given area - are consistent with the methods used to create high-resolution charts of undersea terrain.
Former Australian submarine commander Peter Scott, who served as chief of Australia’s submarine force, said seabed survey data of this type "would be potentially invaluable in preparation of the battlespace" for submarines. "Any military submariner worth his salt will put a great deal of effort into understanding the environment he’s operating in," Scott added.
The spatial focus of the mapping program includes waters around the Philippines, the approaches to Guam and Hawaii, and the seas near Wake Atoll in the north Pacific - all locations of strategic importance because of U.S. and allied military presences. Jennifer Parker, an adjunct professor at the University of Western Australia and a former Australian anti-submarine warfare officer, noted the scale and geographic reach of the effort. "If you look at the sheer extent of it, it’s very clear that they intend to have an expeditionary blue-water naval capability that also is built around submarine operations," she said.
Experts stress that even research explicitly framed as civilian can be integrated into military capability. Under the policy Beijing calls "civil-military fusion," scientific projects and state research can feed technology development and defense planning. Chinese ministries of defense, foreign affairs and natural resources did not provide comment when asked about the seabed mapping and ocean-monitoring activities. U.S. defense officials did not provide comment when asked.
In testimony to a congressional commission this month, Rear Admiral Mike Brookes, the commander of the U.S. Office of Naval Intelligence, described a significant expansion of China’s surveying operations. Brookes said China’s oceanographic efforts are producing data that "enables submarine navigation, concealment, and positioning of seabed sensors or weapons," and that "potential military intelligence collection" by civilian research vessels is a strategic concern.
The United States has recently overhauled its own ocean mapping and monitoring programs, but typically does so with military vessels that can operate with their civilian tracking systems turned off. Chinese vessels operating with a civilian profile sometimes disable their tracking devices as well, a practice that suggests parts of the program may be broader than publicly visible.
Earlier reporting revealed elements of this mapping activity around Guam and Taiwan and in portions of the Indian Ocean. However, the present accounting shows activity across a larger swath of ocean. "It is frankly astonishing to see the enormous scale of Chinese marine scientific research," said Ryan Martinson, an associate professor who studies Chinese maritime strategy. "For decades, the U.S. Navy could assume an asymmetric advantage in its knowledge of the ocean battlespace. China’s efforts threaten to erode that advantage. It is obviously deeply concerning."
Naval analysts emphasize why the specific kinds of data being collected matter in submarine operations and anti-submarine warfare. Hydrographic information helps commanders avoid hazards and find routes of concealment; acoustic conditions determine how sound propagates through water, which is critical for both active and passive sonar. The movement of sound waves is influenced by subsea terrain, and by water temperature, salinity and currents - variables the mapping and sensor networks are designed to monitor.
Tom Shugart, a former U.S. submarine commander, pointed out that acoustic propagation - how sound moves under water - changes with the underwater landscape and with changes in the water column. "Sound waves and submarine movements are also affected by water temperature, salinity and currents," he said. These are the sorts of measurements collected by the arrays deployed as part of China’s ocean observation efforts.
The ships engaged in the campaign are operated by Chinese state institutions - ministries or state-affiliated research bodies - including vessels belonging to the Ministry of Natural Resources and academic institutions. Ocean University’s president has publicly described close ties between the university and China’s navy, as well as the university’s commitment to the construction of maritime capability and national defense. The university did not respond to requests for comment on the mapping and sensor networks.
Geographically, China has prioritized surveys east of the Philippines, an area that lies along the First Island Chain - the sequence of territories, including Japanese islands, Taiwan and parts of Borneo, that forms a maritime boundary between China’s coastal seas and the wider Pacific Ocean. Peter Leavy, a former Australian naval attache to the U.S., said China’s mapping is consistent with concerns about being contained within the First Island Chain. "They’re paranoid about being boxed in to the First Island Chain," Leavy said. China’s mapping, he added, "indicates a desire to understand the maritime domain so they can break out."
Ship-tracking patterns show Chinese mapping operations also near Guam - a site where U.S. nuclear submarines are based - and around Hawaii. The charts also reveal survey work north of a naval base in Papua New Guinea to which the United States has recently gained access, and activity around Christmas Island, an Australian territory that lies on a route between the South China Sea and an important Australian submarine base. In the Indian Ocean, surveys have covered large areas that sit along sea lines of communication China relies on to import oil and other resources.
Jennifer Parker said the surveying in the Indian Ocean points to an expectation that China will conduct more submarine operations there. "China has some key vulnerabilities when it comes to dependencies on maritime trade," she observed. The attention paid to the Ninety East Ridge, an underwater mountain range that crosses an approach to the Malacca Strait, reflects the strategic importance of routes through which much of China’s oil supplies flow.
The program also extends into polar waters. Chinese vessels have surveyed the seabed west and north of Alaska - waters that are part of routes into the Arctic - an area Beijing has signaled it views as a strategic frontier. China has declared an ambition to strengthen its presence in polar regions in coming years.
Observers say the combined mapping and sensor networks are symptomatic of a larger push by Beijing to develop a far-seas naval capability. "This is a manifestation of China’s far-seas reach," said Collin Koh, a maritime security researcher. "They now have a reasonably good picture of the maritime domain they hope to operate in, either in peacetime or in war."
China’s public scientific narrative frames the work in terms of environmental observation and climate science. Around 2014, Wu Lixin, a scientist at Ocean University, proposed a project to create what he called a "transparent ocean" - a network of sensors capable of giving a comprehensive view of water conditions and movement across targeted maritime areas. Provincial officials in Shandong provided initial backing and at least $85 million in support for the project, according to statements by local officials.
The transparent ocean project began in the South China Sea, where Ocean University materials state that an observation system covering the deep-sea basin has been constructed. After surveying the South China Sea, Chinese researchers expanded the project into the Pacific and Indian oceans. Records from the Ministry of Natural Resources, Ocean University and Shandong provincial authorities indicate that hundreds of sensors, buoys and subsea arrays have been deployed east of Japan, east of the Philippines and around Guam to track changes in water temperature, salinity and subsea movement.
In the Indian Ocean, documents from research institutes and government agencies describe deployments surrounding India and Sri Lanka, including instruments placed along the Ninety East Ridge. Ocean University and the Institute of Oceanology, part of the Chinese Academy of Sciences, say the broader sensor network now supplies China with near-real-time information about water conditions and subsea motion.
Some analysts caution that the technical challenge of relaying live data from underwater sensors makes claims of fully real-time awareness difficult, and they urge skepticism about the degree to which all sensors can stream continuous data. Nevertheless, even data that is transmitted with delays has utility. Jennifer Parker said delayed environmental information can still improve a state’s ability to detect the movements of rival submarines and to prepare local forces for undersea operations.
Several of the sensors are placed in locations of tactical sensitivity. Ocean University materials indicate advanced sensor deployments in straits that are known transit routes for submarine traffic, including passages through which U.S. submarines would transit to reach the South China Sea. Chinese scientists describe these installations as monitoring climate and ocean variability, but provincial officials in Shandong explicitly linked the transparent ocean project to maritime defense and security in 2017, comparing it to an American effort to build an ocean sensor network.
Wu Lixin now oversees the expanded observation program through the Qingdao National Laboratory for Marine Science and Technology, which lists, among its partners, China’s Naval Submarine Academy. Wu did not respond to requests for comment. Officials and institutions in Shandong, and national science bodies associated with the work, did not provide comment when asked.
Officials and researchers involved in the deployment view the scientific program as contributing to national defense capabilities. Zhou Chun, an Ocean University researcher who directs sensor arrays in the Indian and Pacific oceans, was quoted in a university press release as saying his work had revealed "the rapid development of my country’s maritime defense and military capabilities." Zhou said he intended to "transform the most advanced scientific and technological achievements into new types of combat capabilities for our military at sea." He did not respond to requests for comment.
Naval analysts view the aggregate effect of seabed mapping, environmental sensors and subsea arrays as creating new operational options for China’s submarines and for undersea surveillance more broadly. The combined data set - bathymetric charts, acoustic environment profiling and sensor networks - provides a baseline for navigation and for acoustic prediction that could be used to either conceal Chinese submarines or to improve the detection of foreign submarines operating in the same waters.
"This is a manifestation of China’s far-seas reach," one maritime-security analyst said, reflecting a view among observers that the mapping and monitoring activity supports Beijing’s ambitions to operate at greater distances from its own coastline. The integration of scientific research, provincial funding and links with naval institutions exemplifies an approach that joins civilian and defense ends in the development of maritime capability.
Limitations and uncertainties remain. Some sensor systems face practical obstacles to continuous, real-time transmission of underwater data. In addition, the full scale of some deployments may be obscured when vessels operate with tracking systems turned off. Analysts caution that where gaps exist in the visible record, those gaps should be acknowledged rather than assumed to indicate specific capabilities beyond what is demonstrably documented.
At the same time, the geographic scope and technical detail of the surveys that are visible in vessel movement records and in scientific literature indicate a deliberate effort to build sustained observational capacity in waters that are strategically important to China and to its principal maritime competitors.
Key takeaways from the documented program include the following: China has mobilized research vessels and sensor networks to collect seabed, hydrographic and oceanographic data across a wide maritime footprint; the collected measures - from bathymetry to temperature, salinity and current profiles - are directly relevant to submarine navigation and acoustic prediction; and the program brings together provincial funding, research institutions and naval partners under a policy framework that encourages civilian-military integration.
Analysts say the outcome of these activities could be an eroding of an asymmetric advantage that navies, particularly the U.S. Navy, historically held in knowledge of undersea operating environments. Officials who have testified before legislative bodies have highlighted the potential for civilian research vessels and sensor networks to provide information that may be used for military decision-making in future conflicts.
Looking ahead, the interplay between scientific oceanography and its application to maritime security will remain a focal point of interest for policymakers and analysts. The balance between open scientific data and strategic considerations will shape how states interpret and respond to expanding observation efforts in the world’s oceans.