MANILA — The Philippines has sent a coast guard ship and an aircraft to confront and escort a Chinese research vessel accused of conducting unauthorized marine scientific research within its exclusive economic zone (EEZ). According to a Monday statement from the Philippine Coast Guard (PCG), the Chinese Research Vessel (CRV) Tan Suo 3 was spotted on May 1, 2025, about 92 nautical miles off the northern Ilocos coast, inside the Philippine EEZ.

The PCG stated that the vessel’s unusual movements suggested marine scientific activities, which violate the Philippines' sovereign rights and are not in line with lawful freedom of navigation. A maritime law enforcement operation was launched to challenge the vessel, successfully stopping its "unlawful activities."

During the operation, the PCG observed a manned deep-sea submersible called Shenhai Yongshi (or Deep-Sea Warrior), which was retrieved by the Chinese ship. This submersible, capable of diving to 4,500 meters, is typically used for deep-sea research missions. The PCG also reported seeing a Rigid Hull Inflatable Boat retrieving a yellow object, believed to be related to marine research. “These actions by the CRV clearly show that the People’s Republic of China is conducting illegal marine scientific research in the Philippines’ EEZ without legal authority,” the PCG said. The Chinese Embassy in Manila has not yet responded to a request for comment.