China’s Ministry of State Security (MSS) has accused foreign intelligence agencies of deploying sensor-equipped marine animals, including fish and turtles, to collect sensitive maritime data in Chinese-controlled waters. The warning was issued in a social media post on Friday, describing what the MSS called an ongoing “unseen covert war” beneath the ocean surface.

According to the MSS, these foreign actors have been using various underwater and surface devices—ranging from buoys and wave gliders to electronic equipment on ships—alongside marine creatures fitted with sensors to gather information. The data targeted includes acoustic signatures of Chinese submarines, naval traffic patterns, and seabed topography. Such intelligence, the MSS said, would pose a significant threat to China’s national security if obtained by adversaries.

In one reported case, “spy turtles and spy fish” were allegedly found carrying sensors that monitored marine environmental conditions such as water temperature, salinity, and ocean currents, transmitting the collected information overseas via satellite in real time. Another example cited involved a solar-powered wave glider, propelled by ocean currents, which was detected transmitting military-related maritime and ship activity data to foreign locations.

China has intensified efforts to combat foreign espionage in recent years, especially in the maritime domain, amid ongoing territorial disputes in the South China Sea. The region remains a flashpoint, with China having militarized reefs and islets contested by several Southeast Asian countries, including the Philippines. In 2024, the MSS reported discovering "underwater lighthouses" used to guide foreign submarines strategically within Chinese waters. Since 2018, Chinese authorities have offered substantial rewards to fishermen who uncover and report spy devices in these areas.

The latest alert comes amid renewed tensions between China and the Philippines over sovereignty claims in the South China Sea. Last month, Philippine Defence Secretary Gilberto Teodoro declared that Manila would defend its territorial and maritime rights against perceived encroachments. Beijing responded by imposing sanctions on Teodoro, barring him from entering China and condemning his statements as damaging to bilateral relations.

While the MSS did not specify which foreign powers were involved in the alleged espionage, the use of marine mammals for intelligence purposes has precedents. In 2023, British intelligence revealed that Russia had deployed trained dolphins in the Black Sea to detect enemy divers near sensitive naval installations. The British Ministry of Defence noted a significant increase in floating enclosures likely intended for bottlenose dolphins, as well as the use of Beluga whales and seals in Arctic waters.

Incidents involving marine animals used for espionage have garnered international attention before. A Russian-labelled whale, nicknamed “Hvaldimir,” was spotted in Norwegian waters in 2019 wearing a camera harness. The whale, believed to have been part of a military program, became a local curiosity before dying in 2024 under circumstances linked to the inability to feed properly due to an injury.

China’s announcement underscores the growing intersection of natural environments and emerging intelligence technologies in the ongoing strategic contest beneath the world’s oceans.