The People’s Republic of China is conducting one of the most ambitious ocean-mapping campaigns in modern military history, deploying a fleet of ostensibly civilian research vessels and hundreds of undersea sensors across the Pacific, Indian, and Arctic oceans to amass the precise environmental data required for submarine warfare against the United States and its allies, according to a sweeping Reuters investigation published today. The findings, drawn from five years of ship-tracking data, Chinese government records, scientific journals, and the assessments of nine naval-warfare experts, lay bare the scale and strategic intent of an operation that strikes at the heart of America’s longstanding advantage beneath the waves.
Reuters reported that it analyzed the movements of 42 Chinese research vessels operating across three oceans using a ship-tracking platform developed by New Zealand firm Starboard Maritime Intelligence, supplemented by an extensive review of Chinese government and university records, journal articles, and scientific studies. The investigation found that the mapping efforts are concentrated in part on militarily critical waters around the Philippines, near the American strongholds of Guam and Hawaii, and near United States military facilities on Wake Atoll in the North Pacific, according to the wire service.
At the center of the operation is the Dong Fang Hong 3, a research vessel operated by Ocean University of China. According to Reuters, the ship spent 2024 and 2025 sailing back and forth near Taiwan and the American garrison at Guam, as well as across strategic stretches of the Indian Ocean. In October 2024, the vessel checked on Chinese ocean sensors capable of identifying undersea objects near Japan, according to Ocean University, and returned to the same area in May 2025. In March 2025, it criss-crossed the waters between Sri Lanka and Indonesia, covering approaches to the Malacca Strait — a critical chokepoint through which much of China’s oil supply passes, Reuters reported.
Yet the Dong Fang Hong 3 is not operating alone. Reuters found that at least eight of the 42 tracked vessels have conducted seabed mapping, while another ten have carried equipment used for that purpose, according to Chinese state media articles, vessel descriptions published by Chinese universities, and government press releases. The survey data, according to Peter Scott, a former chief of Australia’s submarine force, “would be potentially invaluable in preparation of the battlespace” for Chinese submarines, as he told Reuters.
The strategic logic is elementary and grave. Sound propagation — the physics upon which all submarine detection depends — is shaped by seabed terrain, water temperature, salinity, and ocean currents. By charting these variables with unprecedented precision across waters where American submarines operate, Beijing is assembling the environmental intelligence needed both to conceal its own submarines and to hunt those of its adversaries. Naval-warfare experts and United States Navy officials told Reuters that the deep-sea data being collected is giving China a picture of the subsea conditions necessary to deploy its submarines more effectively and to track down those of the United States and allied navies.
In testimony before the U.S.-China Economic and Security Review Commission on March 2, Rear Admiral Mike Brookes, the commander of the Office of Naval Intelligence, confirmed that China had dramatically expanded its surveying efforts, providing data that “enables submarine navigation, concealment, and positioning of seabed sensors or weapons,” according to Reuters. Brookes further stated that “potential military intelligence collection” by Chinese research vessels “represents a strategic concern.” His testimony underscored what the Reuters investigation documented in granular detail: that Beijing’s oceanographic enterprise is not merely academic but constitutes a systematic effort at battlespace preparation.
The investigation also reveals the architecture of China’s undersea surveillance ambitions. Around 2014, Wu Lixin, a scientist at Ocean University, proposed what he termed a “transparent ocean” initiative — deploying networks of sensors to give China a comprehensive view of water conditions and movement through specific areas, according to a statement published by the Chinese Academy of Sciences, as Reuters reported. The proposal received at least $85 million in support from the Shandong provincial government. The project began in the South China Sea, where Ocean University has claimed to have built an observation system covering the deep-sea basin, and has since expanded across the Pacific and Indian oceans.
In 2017, officials from Shandong province said the transparent ocean project was intended to “ensure maritime defense and security” and explicitly compared it with an American military effort to build a United States ocean-sensor network, Reuters reported. Wu now oversees the sensor network through the Qingdao National Laboratory for Marine Science and Technology, whose partners include China’s Naval Submarine Academy, according to the academy’s website, as reported by Reuters. In the Indian Ocean, documents from the Chinese Academy of Sciences and the Ministry of Natural Resources describe a sensor array ringing India and Sri Lanka, including along the Ninety East Ridge — one of the world’s longest undersea mountain ranges, which sits astride the approach to the Malacca Strait, according to the investigation.
The ambition extends to the Arctic. Reuters reported that Chinese vessels have mapped the seabed west and north of Alaska, an essential sea route into the polar region. Beijing has identified the Arctic as a strategic frontier and declared its ambition to become a polar great power by the 2030s, according to the wire service. This Arctic dimension carries particular weight given that modern nuclear submarines can operate for extended periods beneath polar ice, where they become exceedingly difficult to detect — a domain in which the United States has traditionally held commanding advantage.
Chinese researchers themselves have articulated the military implications with unusual candor. Zhou Chun, an Ocean University researcher who oversees the Indian and Pacific ocean sensor arrays, was quoted in a university press release as saying his work had demonstrated “the rapid development of my country’s maritime defense and military capabilities,” according to Reuters. Zhou pledged to “transform the most advanced scientific and technological achievements into new types of combat capabilities for our military at sea,” the wire service reported. He did not respond to Reuters questions.
Collin Koh, a senior fellow in maritime security at Singapore’s RSIS Institute of Defence and Strategic Studies, characterized the scope of the operation in blunt terms. “This is a manifestation of China’s far-seas reach,” he told Reuters. “They now have a reasonably good picture of the maritime domain they hope to operate in, either in peacetime or in war.” Tom Shugart, a former United States submarine commander, described the extensive surveying and Beijing’s growing undersea capability as “symptomatic of China’s rise as a premier maritime power,” according to Reuters.
The investigation noted that while the research has some civilian purposes — including surveying fishing grounds and areas where China holds mineral prospecting contracts — the concentration of effort around American military installations and allied maritime chokepoints leaves little doubt as to the program’s overriding strategic function. China’s civilian survey ships also sometimes disable their tracking systems, meaning the full scope of the campaign may be even greater than Reuters was able to determine. The United States has recently overhauled its own ocean-mapping efforts, but typically conducts such work with military vessels permitted to operate without civilian tracking, Reuters reported.
For the United States, the implications are direct and consequential. For decades, American supremacy beneath the ocean surface has rested on two pillars: the technological excellence of its submarine fleet and an unmatched understanding of the undersea environment in which that fleet operates. China’s systematic campaign to close the knowledge gap — charting the waters around Guam, threading sensors through the approaches to the Malacca Strait, mapping the seabed near Hawaii and Wake Atoll, and pushing into Arctic waters off Alaska — represents a deliberate challenge to both pillars. The question for American defense planners is no longer whether Beijing possesses the ambition to contest the undersea domain, but whether the United States can sustain its advantage in the face of an adversary now charting the battlefield with industrial-scale precision.