China’s fleet has triggered protests from Japan, India and others, but that hasn’t stopped Beijing from launching long missions to map the sea floor. The data they obtain has numerous applications, from science to the emerging industry of deep-sea mining, but it is the Chinese government’s commandeering of civilian research for military use that threatens American allies.

India’s navy drove a Chinese research ship away in 2019, but more have returned. In recent weeks, two of China’s most advanced research vessels, the Xiang Yang Hong 01 and the newer Dong Fang Hong 3 have conducted lawnmower-style sweeps across vast stretches of the eastern Indian Ocean.

Chinese civilian vessels are pursuing expeditions around the world—there are as many as a dozen or so active at any given time. The data they gather, including on currents, temperature and salinity, can have an array of applications. Detailed scanning of the seabed, for instance, can provide information about the visibility of naval mines and the accuracy of sonar.  The surveys can also help determine what minerals could be extracted…Recent missions have spurred complaints by at least half a dozen governments. China says its marine research activities fully comply with the United Nations Convention on the Law of the Sea, the international treaty that established the legal regime for the world’s oceans….

The U.S. Navy also carries out maritime surveys for military purposes…. Under the U.N. convention, coastal states have jurisdiction over research in their exclusive economic zones, which extend 200 miles from the coast. The U.S., which recognizes but hasn’t ratified the convention, argues that military surveys are exempt and U.S. Navy oceanographic ships regularly conduct studies near China. China appears to be moving closer to the American stance, “as they’re doing more oceanographic research without the permission of coastal states.”

Excerpts from Austin Ramzy, China Is Mapping the Seabed to Unlock New Edge in Warfare, WSJ, Mar. 12, 2025