Malacañang, miffed by the unflagging passing of Chinese warships through Sibutu near the Philippines' southernmost province Tawi-Tawi without clearance from the Philippines, wants to know the reason for the ceaseless crossing. Sibutu Passage, a deep channel some 29 km wide that separates Borneo from the Sulu Archipelago, has a deep sill allowing entry of deep water into the Sulu basin while connecting the Sulu Sea with the Sulawesi Sea that feeds from the Pacific Ocean by the Mindanao Current.

Barcelo, V. (2019, August 18). China told: Explain Sibutu intrusions. Manila Standard, pp. A1, A2.