For 21 days, a Chinese marine research vessel remained inside Bajo de Masinloc, or Panatag Shoal, raising questions about what China was studying there, according to Alyansa ng Bantay sa Kapayapaan at Demokrasya chairman Emeritus Jose Antonio Goitia.

Goitia said the Haiyang Dizhi Shi Hao, operated by China’s Guangzhou Marine Geological Survey, stayed inside the shoal from 11 August to 1 September. The vessel is designed for geological surveys that can map the seabed and shallow subsurface.

“A 21-day stay inside the shoal warrants scrutiny, regardless of its stated purpose,” Goitia said.

He cited China’s development of Panganiban Reef, or Mischief Reef, which began with structures described as shelters for fishermen and eventually became an artificial island with military facilities.

“Any single incident might have an explanation. A pattern is harder to wave away,” he said, noting a floating platform spotted at Panatag in May.

Goitia said the Philippines should scrutinize activities that could alter the status quo before they become permanent.