Dozens of Chinese research vessels are on a quest to map the sea floor at strategically vital regions of the world’s oceans. Some of the surveying is for mineral deposits and fishing grounds, but the data the ships collect has a military application. It gives Beijing a detailed picture of the maritime environment in which submarine battles will be waged if conflict erupts, naval experts say.
China is conducting a vast undersea mapping and monitoring operation across the Pacific, Indian and Arctic oceans, building detailed knowledge of marine conditions that naval experts say would be crucial for waging submarine warfare against the United States and its allies.
In one example, the Dong Fang Hong 3, a research vessel operated by Ocean University of China, spent 2024 and 2025 sailing back and forth in the seas near Taiwan and the U.S. stronghold of Guam, and around strategic stretches of the Indian Ocean, ship-tracking data reviewed by Reuters shows. In October 2024, it checked on a set of powerful Chinese ocean sensors capable of identifying undersea objects near Japan, according to Ocean University, and visited the same area again last May. And in March 2025, it criss-crossed the waters between Sri Lanka and Indonesia, covering approaches to the Malacca Strait, a critical chokepoint for maritime commerce.
According to the university, the ship was carrying out mud surveys and climate research. But a scientific paper co-written by Ocean University academics shows it has also conducted extensive deep-sea mapping. Naval-warfare experts and U.S. Navy officials say the type of deep-sea data being collected by the Dong Fang Hong 3 – via mapping and placement of sensors in the ocean – is giving China a picture of the subsea conditions it would need to deploy its submarines more effectively and hunt down those of its adversaries. (Reuters)