Chinese Buoys at Scarborough Shoal

The Philippine Coast Guard on October 15 released photos of two newly installed Chinese buoys at Scarborough Shoal. Coming in the wake of security concerns from South Korea over similar Chinese floating structures in the Yellow Sea, the buoys' installation has raised alarms in Manila over the possibility that Beijing's increasing efforts to assert control over Scarborough could be heading toward a physical occupation of the shoal via the construction of permanent facilities.

Along with the two buoys, the Philippine Coast Guard also found structural debris on the shoal's eastern tip. The Philippine Navy on October 21 identified these as the remnants of Philippine structures installed in the 1980's or 1990's, confirming that no Chinese structures have yet been constructed on the shoal itself.

Collecting Data…

The two buoys installed at Scarborough are of different sizes and designs. The larger buoy installed just outside the shoal's northern tip resembles several buoys identified by the South Korean navy in the Yellow Sea.

Maxar image of 10m buoy at Scarborough Shoal, 10-17-2025

The buoy's dimensions and appearance in both aerial and satellite imagery suggest it is a standardized type of 10-meter ocean environment monitoring buoy. This design is among the "most widely used, oldest, most technologically mature" types of buoy used in China's coastal waters, according to the Shandong Academy of Sciences, which touts their use during the 2008 Olympics as an example.

The other buoy at Scarborough, located inside the lagoon, closely resembles several 2.6- to 3-meter Chinese weather and sea monitoring buoy designs, though more variation appears among these types than the more standardized 10-meter type. At such a small size, this buoy is difficult to observe in satellite imagery.

Each type of buoy seen at Scarbrough is produced by multiplemanufacturers in China and can be outfitted with instruments for collecting a wide variety of marine data, including: "wind speed, direction, temperature, humidity, air pressure, atmospheric CO2 partial pressure, visibility, precipitation, waves, currents, seawater temperature, salinity, turbidity, chlorophyll, dissolved oxygen, seawater CO2 partial pressure, and GPS information." The buoys could be equipped with sensors serving both civilian and military purposes beyond marine science. For instance, sonar equipment, which could detect submarines is not mentioned among the commonly equipped instruments on such buoys but might be useful on the larger one outside the shoal.

…Or Sending a Message?

While the specific sensing equipment on the buoys is difficult to identify without on-site inspection, they are unlikely to provide major new capabilities beyond what China's well-equipped coast guard cutters and frequent naval patrols at Scarborough already offer. But their deployment does communicate several messages on a political level.

Up to now, China has refrained from physically occupying Scarborough. Since a 2012 standoff with the Philippines, it has asserted physical control of the reef entirely through the persistent deployment of coast guard and other vessels. China has sought to further codify that control over the last year, publishing territorial baselines around Scarbrough in December 2024 and declaring a nature reserve on the northeast side of the shoal in September 2025. The installation of semi-permanent, uncrewed buoys is part of this effort to formalize Chinese control over the feature. More worryingly, it is a step toward physically occupying Scarborough, though how big a step is open to interpretation.

The floating and uncrewed nature of these buoys avoids implicit U.S. red lines on reclaiming land or constructing permanent structures on the reef. It will also let Beijing claim that it hasn't violated the 2002 Declaration on the Conduct of Parties in the South China Sea, which bans any occupation of currently unoccupied features. Beijing has vigorously cited that restriction in opposing Philippine efforts to repair the grounded BRP Sierra Madre at Second Thomas Shoal.

Neither the buoys nor Beijing's drawing of baselines has any legal bearing on the sovereignty dispute over the shoal, nor do they affect its legal status or maritime entitlements under the UN Convention on the Law of the Sea. The 2016 South China Sea arbitration found that Scarborough Shoal is a rock entitled only to a 12-nautical-territorial sea, not an exclusive economic zone or continental shelf. The tribunal also found that Philippine traditional fishing rights must be allowed at the shoal, which Beijing has refused to recognize.

Though always possible, a move from China to permanently occupy Scarborough through the construction of fixed structures on the reef would be out of line with the logic of Beijing's recent efforts. Both the deployment of buoys and the declaration of a nature reserve seem carefully crafted to assert Chinese control of the shoal without triggering a major response from Manila, Washington, or others. But with Beijing seemingly determined to administer the waters and skies around Scarborough as Chinese territory in every way short of actual construction, the stage is set for continued frictions as the Philippines endeavors to maintain access.