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The investigation reveals how Chinese scientific vessels were used to map sensitive areas of the seabed, collecting data that could alter the military balance between China, the United States, and allies in the Indo-Pacific.
In October 2024, a Chinese research vessel named Dong Fang Hong 3 was zigzagging through the waters near Guam, the American naval base that houses some of the world’s most powerful nuclear submarines in the Pacific. Officially, the vessel was conducting sediment surveys and climate research for the Ocean University of China. In practice, it was checking a set of underwater sensors installed on the seabed, capable of identifying submerged objects in the depths near Japan.
The scene was neither a coincidence nor an isolated operation. It was part of a systematic, discreet, and long-term campaign that Reuters revealed in March 2026 after five years tracking 42 Chinese research vessels across three oceans: the silent construction of an underwater surveillance infrastructure that U.S. and Australian naval experts describe as potentially decisive in a submarine war — and which China itself calls a “transparent ocean.”
The idea emerged in 2014 at a university, but the Shandong government revealed what it really means
Around 2014, Chinese oceanographer Wu Lixin from the Ocean University of China presented an ambitious project to the Chinese Academy of Sciences: to create a “transparent ocean” through networks of sensors that would monitor in real-time the conditions and movements of waters in specific ocean areas.
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The proposal was presented as scientific research. The stated goal was to better understand oceanic climate, currents, temperature, and sediments. Three years later, in 2017, the government of Shandong province revealed bluntly what the project really meant: the program aimed to “ensure the country’s maritime defense and security.” The explicit comparison was made with a U.S. military effort to build an American network of ocean sensors.
In other words, the same project that entered the world through the portal of science exited through the portal of national defense. And no one stopped the operation.
For a decade, China has built an underwater intelligence infrastructure using universities as cover — and the data collected is as valuable for war as it is for science.
Why the seafloor is the most important battleground of a modern war between great powers
To understand what’s at stake, one must understand the physics of submarine warfare. Sonar — the main submarine detection system — works by emitting sound pulses and measuring how they propagate in water. But the propagation of sound in the ocean directly depends on temperature, salinity, and currents. A detailed map of these variables allows for optimizing sonar to find enemy submarines while also choosing routes where one’s own submarine will be harder to detect.
Rear Admiral Mike Brookes, commander of the U.S. Office of Naval Intelligence, made this explicit in testimony to the U.S. Congress in March 2026: China is building surveillance networks that “collect hydrographic data — water temperature, salinity, currents — to optimize sonar performance and enable continuous surveillance of submarines transiting critical waterways.” Brookes stated that China’s expanded surveys provide data that “enable submarine navigation, camouflage, and the positioning of sensors or weapons on the seafloor” — and classified the operation as a “strategic concern.”
The military logic is simple: a submarine that is not detected is practically invincible. A detected submarine is practically dead. The “transparent ocean” serves both sides of this equation simultaneously.
Knowing the underwater environment better than the adversary is, in underwater warfare, the difference between attacking first and being sunk before realizing.
42 ships, hundreds of sensors, and a mapping grid that covers the world
Reuters tracked 42 active Chinese research ships in the Pacific, Indian, or Arctic Oceans over more than five years, using data from the tracking platform of the New Zealand company Starboard Maritime Intelligence. At least eight of these vessels conducted seabed mapping; another ten carried equipment used for this purpose.
The routes are not random. Many vessels sail in narrow, parallel patterns, similar to grids, associated with systematic ocean floor mapping. It’s the same method a geologist uses to map an oil field — applied to every strategically relevant square kilometer of ocean for Beijing.
The Dong Fang Hong 3 is the most documented case, but it’s not an exception. Between 2024 and 2025, it repeatedly sailed near Taiwan and Guam, crossed the entrances of the Strait of Malacca between Sri Lanka and Indonesia, and checked sensors near Japan. In March 2025, the same ship was mapping the Ninety East Ridge, a submarine mountain range located near the entrances of the Strait of Malacca — the route through which Middle Eastern oil passes to China.
It’s not about scientific curiosity: each mapped area has a strategic address in Chinese military projections.
The sensor map: where China has already installed eyes on the seabed
Records from the Ministry of Natural Resources of China, the Ocean University, and the Shandong government show that hundreds of sensors, buoys, and underwater networks have been installed east of Japan, east of the Philippines, and around Guam. Documents from Chinese scientific institutions describe additional sets of sensors in the Indian Ocean, in areas near India and Sri Lanka.
The mapping goes beyond what would be necessary for scientific research. Chinese vessels have surveyed the waters around Guam — where American nuclear submarines are stationed —, the vicinity of Hawaii, the second-largest US regional military center in the Pacific, an underwater ridge near a naval base in Papua New Guinea to which the US recently gained access, and Christmas Island, an Australian territory on a route between the South China Sea and a vital Australian submarine base.
In the Arctic, the focus is on maritime routes near Alaska, in line with Beijing’s declared ambition to become a major polar power by the 2030s.
From Japan to the Arctic, from Hawaii to the Strait of Malacca, the Chinese network covers exactly the corridors that American submarines would need to use in a conflict in the Indo-Pacific.
The First Island Chain and the fear of being trapped
To understand the strategic motivation, one must know the central geopolitical obsession of the Chinese Navy: the First Island Chain. It is a stretch that extends from the Japanese archipelago to the Philippines and Borneo, functioning as a natural barrier between the Chinese coast and the open Pacific.
In a war with the US, this chain could be used to block the exit of Chinese submarines to the deep waters of the Pacific. Peter Leavy, former Australian naval attaché in the US and president of the Australian Naval Institute, summarized the problem precisely: “They are paranoid about the possibility of being trapped in the First Island Chain.” The mapping of the oceans beyond it “indicates a desire to understand the maritime domain so they can escape.”
Jennifer Parker, professor at the University of Western Australia and former anti-submarine warfare officer, was more direct in analyzing Reuters’ data: “The scale of what they are doing goes beyond resources. If you look at the full extent, it becomes very clear that they intend to have a deep-water expeditionary naval capability built around submarine operations.”
China is not just mapping the ocean. It is mapping the way out of a war.
The civil-military fusion: dual-purpose scientific research
What makes this program legally immune to questioning is the concept Beijing calls “civil-military fusion” — the deliberate integration between scientific research, technological development, and defense objectives. The ships are operated by universities. The data is published in scientific journals. The sensors are presented as climate observation tools. Everything is legal. And everything also serves war.
The most revealing admission came from within the system itself. Zhou Chun, a researcher at the Ocean University who oversees sensor networks in the Indian and Pacific Oceans, was quoted in an institutional statement saying that his work showed him “the rapid development of my country’s maritime and military defense capabilities.” He promised “to transform the most advanced scientific and technological achievements into new types of combat capabilities for our military forces at sea.”
It was not a leaked secret statement. It was an official statement from a Chinese university.
China’s Ministries of Defense, Foreign Affairs, and Natural Resources did not respond to Reuters’ questions. The U.S. Department of Defense also did not respond.
A university researcher publicly promises to convert oceanographic data into combat capability, and the world continues to call the ships “scientific vessels.”
What the U.S. lost and what they are trying to recover
For decades, superior knowledge of the ocean environment was one of the most secretive and decisive advantages of the American Navy. This dominance allowed its submarines to operate with greater secrecy, effectiveness, and unpredictability than any adversary. China is systematically closing this gap.
Peter Scott, former head of Australia’s submarine force, was direct in assessing Reuters’ data: the surveys by Chinese ships “would be potentially invaluable in preparing the battlefield” for Beijing’s submarines. “Any military submariner worth their salt puts enormous effort into understanding the environment in which they operate.”
The U.S. has been reshaping its own ocean mapping efforts, but typically does so with military ships legally restricted to international waters. China uses universities to cover what military ships cannot or should not — creating scientific cover for strategic intelligence gathering on a global scale.
The American advantage in knowledge of the underwater environment lasted for decades. China spent a decade quietly building the infrastructure to eliminate this advantage.
The connection with the Indonesian torpedo and the cut submarine cables
The “transparent ocean” network does not exist in isolation. In April 2026, an Indonesian fisherman found in the Lombok Strait, one of the few deep corridors of the archipelago where submarines can transit submerged between the Pacific and Indian oceans — a metallic torpedo-shaped object identified as a Chinese submarine monitoring system. It was literally a sensor from this same network.
In parallel, in April 2026, China successfully tested a machine capable of cutting submarine cables at a depth of 3,500 meters using a diamond disc — exactly the depth where the communication cables connecting American naval command centers are located.
The three elements form a coherent strategy: map where the adversary submarines are, monitor their movements in real-time, and, if necessary, cut the communication that commands them.
The ocean is no longer a neutral space between powers. In the last ten years, it has become a prepared battlefield, and China has worked the most to understand the terrain.
And you, did you know that research vessels from Chinese universities spent years mapping the seabed near the world’s largest American naval bases? Were you impressed to discover that the researcher responsible for the sensors publicly promised to use the data for military purposes? Leave your comment, tell us what you found most revealing, and share with those who follow geopolitics, defense, and naval technology.
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