The Asian Maritime Transparency Initiative (AMTI) said the presence of Chinese Coast Guard (CCG) vessels at Bajo de Masinloc (Scarborough Shoal) sharply surged during the first half of 2026, nearly matching the total patrol activity recorded for all of 2025.

Using automatic identification system (AIS) data collected from 1 January to 30 June, AMTI found that CCG vessels accumulated 933 ship-days around Bajo de Masinloc during the six-month period, close to the 1,099 ship-days logged throughout 2025.

The 2025 figure had already more than doubled the 516 ship-days recorded in 2024.

AMTI said monthly CCG patrols averaged 156 ship-days in the first half of 2026, up from 90 ship-days during the same period last year. Patrol activity peaked in May with 216 ship-days.

Chinese coast guard vessels have expanded their patrol coverage around the shoal, with multiple ships coordinating to maintain a perimeter extending roughly 30 nautical miles from Bajo de Masinloc.

Six to eight Chinese maritime militia vessels also maintained a near-continuous presence closer to the shoal.

The report stated that some Chinese coast guard ships continued patrolling along — and at times beyond — China's self-declared nine-dash line to intercept Philippine vessels heading toward the disputed feature.

Philippine maritime patrols also increased during the period but remained significantly lower than China's.

The Philippine Coast Guard and the Bureau of Fisheries and Aquatic Resources recorded an average of 43 ship-days per month during the first half of 2026, a 43-percent increase from the 30 ship-days per month logged during the same period in 2025.

The heightened maritime activity resulted in more frequent encounters between Chinese and Philippine vessels. AMTI documented interactions between CCG and Philippine vessels on 112 days during the first six months of the year, averaging 19 days each month.

Among the incidents cited by the group was a May 27 encounter involving Chinese Coast Guard vessel CCG 21563 and the Philippine vessel BRP Datu Pagbuaya.

Satellite imagery also detected additional ships in the area that were not broadcasting AIS signals.

AMTI also pointed to China's increasing use of floating installations at Bajo de Masinloc.

Philippine authorities on May 25 discovered a 6-by-6-meter floating platform inside the lagoon, prompting Manila to file a diplomatic protest. Chinese officials later described the structure as a temporary research facility intended to collect ecological data.

The platform's deployment coincided with the operations of the Chinese research vessel Xiang Yang Hong 33, which conducted surveys around Bajo de Masinloc after carrying out research missions in several reefs in the Spratly Islands.

Although the floating research platform was removed on 17 June, AMTI noted that other Chinese floating objects, including two buoys installed in October 2025 and several additional floating objects identified by Philippine authorities in May, remain in the area.

The report said the level of Chinese coast guard activity at Bajo de Masinloc during the first half of 2026 was the highest recorded by AMTI since it began tracking AIS data in 2019.

While Beijing has not undertaken land reclamation or built permanent structures at the shoal, it has increasingly employed coast guard patrols, maritime militia deployments, floating installations, and civilian research activities to strengthen its presence and control over the disputed feature.

These developments, AMTI said, suggest China is testing new ways to reinforce its claims over Bajo de Masinloc while avoiding actions that could trigger stronger international responses.