A suspected underwater drone with Chinese markings was found by local fishermen in coastal waters off Linapacan, Palawan, the Philippine Coast Guard (PCG) confirmed Tuesday, Sept. 30, raising fears that it may have been used in illegal marine research in Philippine waters.

The approximately 12-foot-long device was discovered by fishermen in the vicinity waters of Barangay Barangonan last Sept. 28. They immediately turned it over to PCG Station Linapacan for further verification, technical examination, and investigation, said PCG spokesperson for West Philippine Sea (WPS) Commodore Jay Tarriela.

“Preliminary observations show that the device features a Conductivity-Temperature-Depth (CTD) sensor—a compact probe designed to measure seawater salinity, temperature, and depth, which are key parameters for oceanographic profiling,” Tarriela noted.

He said the sensor had the Chinese label “海水盐度传感器”, which translates to “seawater salinity sensor” in English, a device used to measure the salt concentration or salinity in seawater.

It also has the serial number (CTD-20090334), which could mean that the device was a conductivity, temperature, and depth sensor manufactured in 2009 with a unique serial or production number “0334.”

The drone also had visible corrosion from prolonged saltwater exposure, Tarriela noted, and was mounted on a rugged metal frame which is “typical of components in autonomous underwater vehicles commonly known as underwater drones.”

“This incident highlights ongoing illegal marine scientific research in Philippine waters amid a pattern of similar events involving foreign-origin autonomous underwater vehicles (AUVs),” Tarriela revealed.

Since 2022, at least five incidents of underwater drone recoveries have been recorded by the PCG. These were in Pasuquin, Ilocos Norte (July 2022); off the coast of Zambales (September 2022); Calayan Island, Cagayan (August 2024); Initao, Misamis Oriental (October 2024); and San Pascual, Masbate (December 2024).

Tarriela said at least three of those prior recoveries “have been linked to Chinese deployment, based on evidence such as China Telecom SIM cards, iridium transceivers connected to Beijing-based HWA Create (a defense contractor), and battery packs marked by China Electronics Technology Group Corporation.”

“Previous forensic analyses of similar recovered AUVs have identified them as tools for advanced underwater surveillance and seafloor mapping. The integrated CTD sensor allows for the collection of data on salinity, temperature gradients, depth, and acoustic propagation—essential for bathymetric charting and environmental monitoring,” Tarriela said.

“Recovered units have shown capabilities for autonomous data processing, storage, and satellite transmission, with one case revealing encrypted communications to mainland China during operations,” he stated.

The PCG said the device was undergoing a detailed forensic examination to determine its exact origin, operational history, and potential security risks.

The PCG urged the public to report any suspicious maritime objects to the nearest Coast Guard station.

“The Philippine Coast Guard remains vigilant in safeguarding our maritime domain and protecting the livelihoods of our fisherfolk. We commend the quick action of the local fishermen for reporting this find. This incident highlights the need for continued community awareness and a whole-of-nation approach to deter unauthorized activities in our waters,” PCG Commandant Adm. Ronnie Gil Gavan said.