© Getty Images Including reconnaissance conducted near US naval bases.
China is undertaking a substantial underwater mapping and observation campaign throughout the Pacific, Indian, and Arctic oceans, accumulating in-depth understanding of marine environments that naval specialists suggest will be vital in the instance of a submarine battle against the United States and its partners, Reuters reveals.
While some research is geared toward discovering mineral wealth and fishing locations, the data gathered by these vessels also presents military utility.
As an illustration, ship-tracking information analyzed by Reuters demonstrates that a research vessel managed by the Ocean University of China navigated the waters off Taiwan and the U.S. territory of Guam, along with key portions of the Indian Ocean, in 2024 and 2025. In October 2024, it assessed potent Chinese oceanic sensors skilled at identifying underwater objects near Japan, revisiting the same area last May. Furthermore, in March 2025, it traversed the waters between Sri Lanka and Indonesia, covering approaches to the Strait of Malacca, an essential chokepoint for maritime traffic.
According to the Ocean University of China, the vessel conducted sediment and climate inquiries. Nevertheless, a scholarly article co-authored by university scientists reveals that it also engaged in considerable deep-sea mapping. Naval operation authorities and U.S. Navy personnel indicate that the deep-sea information acquired by the Dong Fang Hong 3 — via mapping and placement of oceanic sensors — furnishes China with awareness of underwater conditions, crucial for improved deployment of submarines and hunting of enemy submarines.
Consequently, the magnitude of exploration pertains not solely to resources, but additionally holds expeditionary naval capacity, rooted in submarine operations.
The Dong Fang Hong 3 does not operate alone. It constitutes a portion of a broader oceanic mapping and surveillance endeavor, involving numerous research vessels and hundreds of sensors. To monitor this initiative, Reuters scrutinized Chinese governmental and university documents, incorporating journal publications and scientific studies, and evaluated over five years of movement from 42 research ships functioning in the Pacific, Indian, and Arctic oceans.
While officially intended for civilian purposes — with certain surveys encompassing fishing regions or locales where China possesses mineral prospecting agreements — the endeavor holds military applications, according to nine naval specialists who assessed the findings with Reuters.
In order to collect insights concerning the underwater topography, research ships chart the seabed by maneuvering back and forth in tightly spaced lines. Tracking information highlights this pattern of vessel movement spanning expansive zones of the Pacific, Indian, and Arctic oceans.
Records show that a minimum of eight ships observed by Reuters were conducting seabed mapping, and an additional ten were carrying equipment employed for mapping purposes.
Former Australian submarine commander Peter Scott considers that the research information obtained by the ships “will be potentially invaluable in preparing the battlespace” for Chinese submarines.
He also remarked, “Any military submariner will dedicate significant efforts to comprehend the environment in which they operate.”
Vessel tracking data reveals that China’s seabed exploration efforts are partially centered on militarily relevant waters surrounding the Philippines, near Guam and Hawaii, and in proximity to U.S. military facilities situated on Wake Atoll in the North Pacific.
Experts highlight that even when data is gathered for scientific purposes, the blending of civilian scientific research with military technology development has evolved into a core focus of the Chinese government, referred to by Beijing as “civilian-military fusion.”
Recently, Rear Admiral Mike Brooks, leader of the US Office of Naval Intelligence, testified before a congressional assembly, noting that China has considerably broadened its geodetic surveying ventures. He also stated that the “potential military intelligence collection” by Chinese survey vessels “poses a strategic concern.”
The United States has recently revamped its own schemes for mapping and overseeing the ocean, typically employing military ships authorized to deactivate tracking systems regulated by civilian software. Chinese civilian reconnaissance vessels also periodically disable tracking, implying their operation may extend further.
“For several decades, the U.S. Navy has been fortunate to leverage an uneven advantage via its knowledge of the oceanic battlespace. However, China’s actions jeopardize the undermining of that edge. This is manifestly deeply concerning,” commented Ryan Martinson, a scholar specializing in Chinese maritime strategy at the U.S. Naval War College.
Naval experts assert that the data amassed by Chinese research vessels concerning the seabed and water environments is critical for both submarine deployment and anti-submarine measures. Captains necessitate details pertaining to underwater topography in order to avert collisions and obscure their vessels.
Nevertheless, the information also holds significance in spotting submarines operating within a few hundred meters of the surface. Submarines are often distinguished by their sound emissions or the reverberations of signals transmitted by sonar. The transit of these sound waves, however, fluctuates contingent on the underwater terrain, water temperature, salinity, and currents.
China has already executed its most thorough oceanographic surveying east of the Philippines, surrounding Guam, where specific U.S. nuclear submarines are positioned, adjacent to Hawaii, investigated an underwater ridge north of a U.S. naval installation in Papua New Guinea, and executed reconnaissance operations encircling Australia’s Christmas Island. Furthermore, Chinese vessels have mapped the seabed west and north of Alaska, a crucial marine passageway leading to the Arctic.
As far back as 2014, China initiated a scheme in the South China Sea to develop a “transparent ocean” through deployment of sensors, providing a full depiction of water status and its displacement through particular zones, establishing an extensive deep-sea surveillance network.
After exploring the South China Sea, Chinese scientists have widened the Transparent Ocean Project to encompass the Pacific and Indian Oceans. China has positioned hundreds of sensors, buoys, and underwater arrays within the Pacific Ocean, aimed at pinpointing alterations in water conditions, namely temperature, salinity, and underwater movement. Within the Indian Ocean, they have similarly positioned a sensor array extending across India and Sri Lanka.
The Ocean University and the Institute of Oceanology, an entity within the Chinese Academy of Sciences, conveyed that a broader sensor network now furnishes China with current details regarding water conditions and underwater movement.
While Chinese scientists assert that these sensors monitor climatic shifts and marine conditions, Shandong provincial authorities indicated in 2017 that the Transparent Ocean Project was purposed to “ensure maritime defense and security,” directly drawing comparisons between the endeavor and the U.S. military’s efforts to establish an American ocean sensor network.
Collective mapping and monitoring afford China advanced instruments for detecting rival submarines and deploying their own within some of the globe’s most disputed waters.
Collin Koh, a senior fellow on maritime security at the Singapore Institute of Defence and Strategic Studies (RSIS), asserts that this embodies China’s imprint on the high seas. He further elaborated that they now possess a rather precise comprehension of the maritime environment in which they anticipate operating, during both times of peace and times of conflict.