SCARBOROUGH SHOAL, South China Sea — We could see the glistening turquoise waters in the distance, a haven where deep-sea waves soften and, fishermen say, the grouper and snapper could feed a village for eternity.

But guarding the waters, the mouth of Scarborough Shoal, was a 130-foot Chinese Coast Guard ship. If we were to get more than a glimpse of this speck of coral and rock — the latest potential point of contention between China and the United States in the South China Sea — our boat would have to be quick.

Capt. Alex O. Tagapan, who usually takes tourists on sightseeing cruises, steered toward the entrance of the boomerang-shaped atoll and accelerated. Turning to a small statue of Santo Niño de Cebú, a patron saint of the Philippines known for miraculous powers, he prayed.

Within minutes, the Chinese sent a speedboat painted with the coast guard’s red stripes racing toward us. “Get out! Get out!” a man on the boat wearing a bamboo hat and an orange vest shouted in English, waving his arms.