China has launched a covert but expansive operation across the Pacific, Indian, and Arctic Oceans, focusing on detailed seabed mapping and the deployment of underwater monitoring networks. Analysts argue that precise knowledge of the ocean floor is indispensable for submarine warfare, particularly in regions dominated by the United States and its allies.
Satellite and vessel tracking data reviewed by Reuters indicate that the Chinese research ship Dong Fang Hong-3, operated by Ocean University of China, repeatedly navigated strategically sensitive waters near Taiwan and the US military base in Guam during 2024 and 2025. The vessel was also observed in key areas of the Indian Ocean.
According to Ocean University, China has installed advanced sensor networks off Japan’s coast capable of detecting any underwater movement. In October 2024, Dong Fang Hong-3 maintained these systems and collected data, strengthening surveillance over US and allied submarines. The vessel returned in May 2025, and in March 2025, it charted waters between Sri Lanka and Indonesia, a critical gateway to the Malacca Strait, one of the world’s busiest maritime trade routes.
Naval experts note that repetitive, parallel movements in a defined area typically indicate efforts to create a highly precise 3D map of the seabed. While the university maintains that the vessel’s work is purely scientific—examining sediments and oceanographic conditions—published research by its scientists confirms comprehensive seabed mapping activities.
Key Movements of Dong Fang Hong-3
| Year | Region | Activity | Strategic Significance |
|---|---|---|---|
| 2024 Oct | Near Japan | Sensor maintenance & data collection | Monitor US/allied submarine movements |
| 2025 May | Same area | Follow-up surveillance | Validate sensor network efficiency |
| 2025 Mar | Sri Lanka–Indonesia waters | Zigzag survey | Control over Malacca Strait access |
Dong Fang Hong-3 is part of a broader initiative involving dozens of research vessels and hundreds of sensors. Reuters, with assistance from a New Zealand-based firm, analysed the five-year movements of 42 vessels and reviewed official Chinese scientific documentation. Nine naval specialists confirmed that while some activities are framed as civilian research, the underlying objective is military. At least eight vessels are directly engaged in seabed mapping, with ten others equipped with full mapping technology.
Australian former submarine chief Peter Scott emphasised the strategic value: “Detailed seabed knowledge is invaluable for submarine operations. A skilled commander must understand the underwater terrain fully.”
This extensive Chinese maritime surveillance spans Philippine waters, areas around Guam and Hawaii, and the northern Pacific near Wake Island. Experts, including Jennifer Parker of the University of Western Australia, assert that such scale indicates China’s ambition to develop a deep-sea capable navy centred on submarines. Chinese efforts blend civilian research and military capability under the “civil-military fusion” strategy championed by President Xi Jinping.
The programme, named ‘Transparent Ocean’, was initiated in 2014 with funding exceeding US$85 million. Initially focused on the South China Sea, it has now expanded across the Pacific and Indian Oceans, deploying sensors and drones around Japan, the Philippines, Guam, India, and Sri Lanka. Special attention is given to the Ninety East Ridge and Malacca Strait—the primary route for Chinese oil imports.
Experts warn that sensor placement in sensitive routes frequently used by US submarines represents a significant strategic advantage. Chinese officials, while framing the initiative as climate and oceanographic research, have acknowledged its security purpose. The Naval Submarine Academy is a key collaborator, integrating scientific data into tactical applications.
Submarine warfare experts, including former US commander Tom Shugart, contend that China’s mapping and surveillance activities indicate the nation’s growing maritime power and capacity for submarine operations across contested waters. Singaporean analyst Colin Koh adds that these capabilities provide China with a clear operational picture in both peacetime and conflict scenarios.
By converting scientific achievement into operational readiness, China is now poised to exert unprecedented influence over critical maritime domains, enhancing both surveillance and strategic deployment of its submarine fleet.