China mapping ocean around India to avert its own Hormuz moment in Strait of Malacca?

China is carrying out an extensive ocean-mapping and monitoring programme across the Pacific, Indian and Arctic oceans, collecting data that naval experts believe could significantly enhance its submarine warfare capabilities against the United States and its allies. The effort, involving dozens of research vessels and hundreds of underwater sensors, is not limited to scientific research. A new detailed investigation by Reuters says the scale and pattern of activity indicate a dual-use strategy – civilian on the surface but with clear military applications beneath.

At the heart of this push lies a strategic concern long associated with Beijing: securing critical sea lanes, particularly through the Strait of Malacca, and reducing vulnerabilities in the event of a conflict that could threaten its energy and trade lifelines. This vulnerability has a direct bearing on India’s strategic calculus as well. Located astride key Indian Ocean routes and in proximity to the Malacca chokepoint, India is widely seen as capable of influencing or even restricting access in a conflict scenario, a risk often described as China’s “Malacca dilemma”. China’s expanding undersea mapping and surveillance efforts, including in waters around India and Sri Lanka, are therefore increasingly viewed as part of a broader attempt to reduce this dependence and counter any potential blockade by regional adversaries.A vast, coordinated mapping operationData reviewed by Reuters shows that at least 42 Chinese research vessels have been actively surveying key maritime regions over the past five years. Among them, the Dong Fang Hong 3, operated by Ocean University of China, conducted repeated missions near Taiwan, Guam and across strategic stretches of the Indian Ocean between 2024 and 2025.The vessel’s movements, sailing in tight, grid-like patterns, indicate systematic seabed mapping. It also checked on underwater sensor arrays near Japan and criss-crossed waters between Sri Lanka and Indonesia, covering approaches to the Malacca Strait.

While Chinese institutions describe such missions as “mud surveys” or climate research, a scientific paper cited by CNN confirms extensive deep-sea mapping activity. Strategic experts say this kind of data is crucial for military planning. Peter Scott, a former chief of Australia’s submarine force, told Reuters the survey data “would be potentially invaluable in preparation of the battlespace” for submarines.Why mapping the seabed matters in warfareModern submarine operations rely heavily on understanding underwater terrain and oceanographic conditions. Factors such as seabed topography, water temperature, salinity and currents influence how sound travels underwater, critical for both detecting and evading submarines.Tom Shugart, a former US submarine commander, previously noted that sonar performance and submarine detection depend on how sound waves interact with the underwater environment.Rear Admiral Mike Brookes of the US Office of Naval Intelligence told a congressional panel that such data enables “submarine navigation, concealment, and positioning of seabed sensors or weapons.”In practical terms, this means better stealth for Chinese submarines and an improved ability to track adversaries.‘Transparent ocean’: China’s sensor network ambitionChina’s mapping efforts are part of a broader initiative to build what it calls a “transparent ocean”, a network of sensors, buoys and subsea arrays that provide real-time data on ocean conditions.First proposed around 2014 by Chinese scientist Wu Lixin, the project received at least $85 million in funding and began in the South China Sea before expanding to the Pacific and Indian oceans.According to Chinese academic and government records cited in a report, hundreds of sensors have been deployed in areas east of Japan, around Guam, and near the Philippines, regions critical to US naval operations.

In the Indian Ocean, similar sensor arrays have been placed around India and Sri Lanka, including along the Ninety East Ridge, a key underwater feature near the Malacca Strait.While officially framed as scientific infrastructure, Chinese officials have linked the project to “maritime defence and security.”Focus on strategic chokepointsA key pattern in China’s mapping effort is its concentration around critical maritime chokepoints and military hubs.These include:

Jennifer Parker, a defence expert at the University of Western Australia, told Reuters: “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.”The ‘Malacca dilemma’ and China’s strategic anxietyChina’s dependence on the Malacca Strait has long been viewed as a strategic vulnerability, often referred to as the “Malacca dilemma,” and for years has been its most pressing Achilles’ heel. A significant portion of China’s energy imports from the Middle East and Africa passes through this narrow chokepoint. In a conflict scenario, adversaries could potentially disrupt these supply lines.This explains Beijing’s increasing focus on:

Peter Leavy, a former Australian naval attaché, told Reuters China is “paranoid about being boxed in” within the First Island Chain, highlighting its desire to break out into deeper waters.What explains China’s paranoia The ongoing war in the Middle East saw Iran exercising its biggest leverage against the West, its ability to control the Strait of Hormuz, a critical waterway through which passes over 20% of global energy supply. Countries from across Asia and beyond, either directly or indirectly, have suffered the repercussions of an Iranian blockade in the Strait, where a narrow maritime passage can be blocked or militarily controlled, crippling energy and trade flows. For China, that equivalent vulnerability lies at the Strait of Malacca.

The Strait of Malacca is not just one of the world’s busiest shipping lanes, it is the single most critical maritime artery for global energy trade. According to the latest EIA World Oil Transit Chokepoints analysis, the strait carried about 23.2 million barrels per day of oil in the first half of 2025, accounting for nearly 29% of total global seaborne oil flows. This makes it the largest oil chokepoint in the world by volume, surpassing even the Strait of Hormuz. In addition, around 9.2 billion cubic feet per day of liquefied natural gas (LNG) transited through the route during the same period. For China, the significance of Malacca is even more pronounced. As per Observer Research Foundation (ORF) estimates, China’s energy imports touched about $390 billion in 2024, with nearly 80%, roughly $312 billion worth, passing through the Malacca Strait. The corridor serves as the shortest and most efficient sea link between energy producers in the Middle East and consumers in East Asia, making it indispensable for sustaining China’s industrial economy and trade flows.A narrow sea lane, which China does not control, could become a chokepoint in times of conflict. Any disruption in this corridor would have immediate consequences for China’s energy security, manufacturing output, and broader economic stability.

In response, China has attempted to mitigate this vulnerability through diversification, investing in overland pipelines, expanding connectivity under the Belt and Road Initiative, and developing port networks across the Indian Ocean, sometimes described as the “String of Pearls”. However, these alternatives remain limited in scale and efficiency. None can fully match the speed, capacity, and cost advantages of the Malacca route, leaving China structurally exposed to potential maritime disruption.India’s role in the Indian Ocean equationFor India, China’s activities in the Indian Ocean, particularly near Sri Lanka and critical sea lanes, carry clear strategic implications.India sits close to the Malacca Strait and has long been seen as a potential gatekeeper in the region. Its Andaman and Nicobar Command provides a vantage point over key shipping routes.Over the years, India has:

These measures are partly aimed at maintaining leverage over vital sea lanes, including the Malacca Strait.China’s increased mapping activity near these waters suggests it is preparing for scenarios where access could be contested.Civil-military fusion at playA defining feature of China’s approach is the integration of civilian research and military objectives, a strategy Beijing calls “civil-military fusion.”Research vessels operated by universities and state agencies are involved in mapping missions, but their findings can be used for defence purposes.Ryan Martinson of the US Naval War College talking to CNN described the scale of Chinese marine research as “astonishing,” warning that it could erode the US Navy’s long-standing advantage in undersea knowledge.Global reach: From Pacific to ArcticChina’s ambitions extend beyond the Indo-Pacific. Its vessels have also mapped seabed areas near Alaska and Arctic sea routes, aligning with its goal of becoming a “polar great power” by the 2030s.This global footprint reflects a broader shift: China is positioning itself as a major maritime power with the ability to operate far from its shores.Collin Koh, a maritime security expert in Singapore, told Reuters: “They now have a reasonably good picture of the maritime domain they hope to operate in, either in peacetime or in war.”What it means going forwardChina’s ocean-mapping campaign signals a long-term strategic shift rather than a short-term tactical move.By combining scientific research with military planning, Beijing is building a detailed understanding of the underwater domain, one that could shape future naval conflicts.For India, the implications are immediate. Increased Chinese presence and data-gathering in the Indian Ocean could challenge its traditional advantage in the region.For the US and its allies, the concern is broader: a potential narrowing of the undersea intelligence gap that has historically favoured Western navies.As competition moves beneath the surface, the oceans are becoming a critical frontier, not just for trade and resources, but for strategic dominance in an increasingly contested maritime world.