Upon the directive of PCG Commandant Admiral Ronnie Gil Gavan, the Philippine Coast Guard (PCG) deployed an aircraft and vessels to challenge and disrupt the illegal marine scientific research (MSR) of the Chinese research vessel TAN SUO YI HAO (MMSI 413523770, IMO 8315451, call sign BJLJ), which is operating without authorization inside the Philippine Exclusive Economic Zone (EEZ) in the vicinity of Hubo Reef (Hardy Reef) in the West Philippine Sea.
Through Dark Vessel Detection (DVD) and AIS tracking, the PCG established that the vessel departed the vicinity of Sanya, Hainan on 02 October 2026, transited the western side of the South China Sea, and entered the Philippine EEZ at 7:30 PM on 09 October 2026. On the morning of 10 October 2026, it was lying-to approximately 12 nautical miles northwest of Katimugan Bank, and declared through its AIS that it was engaged in diving operations with restricted maneuverability, while directing other vessels to keep two nautical miles clear. It also declared an estimated time of arrival of 17 October 2026, indicating its intent to remain in the area for at least another week.
The vessel subsequently went silent on AIS before resuming transmission. As of 1:45 PM on 11 October 2026, TAN SUO YI HAO was underway approximately 5.63 nautical miles west-northwest of Hubo Reef and 116.72 nautical miles northwest of Rizal, Palawan, still declaring restricted maneuverability and diving operations.
TAN SUO YI HAO is operated by the Institute of Deep-sea Science and Engineering of the Chinese Academy of Sciences, based in Sanya. It serves as a mothership for China’s deep-sea manned submersibles, including the Fendouzhe, and is equipped with deep-sea winches, sounding systems, and sediment collection devices for seabed investigation. It is the first among the Chinese research vessels recently monitored by the PCG to openly declare diving operations inside the Philippine EEZ, and the one operating farthest into the southern portion of the West Philippine Sea.
On the morning of 11 October 2026, a PCG Islander aircraft conducted a Maritime Domain Awareness (MDA) flight from Antonio Bautista Air Base in Puerto Princesa City. At 8:13 AM, the aircrew located TAN SUO YI HAO approximately five nautical miles west-northwest of Hubo Reef, slowly navigating eastward. No deployed submersible, equipment, or lines were observed in the water at the time of the overflight. The PCG aircraft issued multiple radio challenges to the Chinese research vessel, all of which went unanswered.
During the same flight, the PCG aircraft also monitored China Coast Guard vessel CCG 5306 approximately 6.8 nautical miles south of Hubo Reef, and another China Coast Guard vessel approximately 12.7 nautical miles southwest of Hubo Reef. Two People’s Liberation Army Navy vessels were likewise monitored in the surrounding waters, one approximately 22.8 nautical miles northeast of Escoda Shoal and the other approximately 11.3 nautical miles south-southeast of Katimugan Bank.
Following the results of the MDA flight, Admiral Gavan ordered the deployment of PCG vessels to the area to directly challenge TAN SUO YI HAO and disrupt its illegal MSR activities within the Philippine EEZ.
The Department of Foreign Affairs has confirmed that no request for consent was received from China for any marine scientific research to be conducted by TAN SUO YI HAO in the Philippine EEZ.
