Filipino fisherman Mariel Villamonte had spent years scouring the turquoise waters of the South China Sea’s Scarborough Shoal for snapper and grouper — until a Chinese Coast Guard vessel fired water cannons at his boat.

That was in 2012, around the time China wrested control of the small reef ring from the Philippines, and he didn’t dare go back.

“Their ships are made of steel, ours are made of wood,” said Villamonte, now 31, recalling how two Chinese ships chased his boom before blasting it with high-pressure water.

The fishing ground, being explored by generations of Filipinos, is one of many potential flashpoints for military conflict in the South China Sea.

China and Taiwan both claim sovereignty over most of the sea, while the Philippines, Vietnam, Malaysia and Brunei have competing claims to parts of it.

Trillions of dollars worth of shipping trade pass through the waterway annually, and naval vessels of the United States and Western allies pass through it regularly.

Of all the plaintiffs, China has been the most aggressive in enforcing its stance in recent years.

Hundreds of China Coast Guard and Maritime Militia vessels roam the waters, swarming reefs, harassing and attacking fishermen and other boats, and interfering with oil and gas exploration and scientific research.

Analysts say Beijing’s goal is regional supremacy and control of all activity in the waters — and it’s using its power to force smaller rivals into submission.

“They really envision being the center of this region economically, politically and militarily,” said Jay Batongbacal, director of the University of the Philippines Institute of Maritime Studies and Law of the Sea.

“What they want is that at some point the weaker nations just give up and leave them there just to avoid a problem.”

China often invokes the so-called nine-dash line, a vague delineation based on maps from the 1940s, to justify its claims to the South China Sea.

The Philippines brought a case before an international court to challenge China’s stance. The tribunal ruled in 2016 that Beijing’s demands had no legal basis.

China has since ignored the ruling, and tensions with the Philippines eased after former President Rodrigo Duterte rescinded his country’s legal victory and instead courted Chinese companies.

Ferdinand Marcos Jr., who took over from Duterte in June this year, has pledged to uphold the court decision and insisted he would not allow China to trample on Manila’s maritime rights.

But in the decade under President Xi Jinping, who is expected to take office for the third straight month this month, China has dramatically increased its presence in the sea.

Xi’s desire for control of the waters is not about fish or fossil fuels, said Greg Poling, director of the US-based Asia Maritime Transparency Initiative (AMTI).

His main goals are to realize the “Chinese Dream” of national revitalization — Xi’s vision of restoring the country to its supposed past glory — and to secure its political legitimacy.

Poling said generations of Chinese leaders have made increasingly “absurd” claims to the sea, leaving Xi with no choice but to “make claims on everything.”

Satellite images released by AMTI show that China’s land reclamation efforts in the waters have far outpaced all other claimants combined.

Since 2013, it has demolished about 6,000 hectares (15,000 acres) of reef to create about 1,300 hectares of new land for artificial islands in the Spratly archipelago, Poling said.

The militarized islands – complete with airstrips, ports and radar systems – allow Chinese ships to patrol as far away as Indonesia and Malaysia.

Aside from destroying fish hatcheries and suffocating marine life with sediment, experts say Beijing’s actions violate international law.

Under the 1982 United Nations Convention on the Law of the Sea, which China helped negotiate, countries have exclusive rights to natural resources within about 200 nautical miles of their shores.

China’s claims go up to a thousand nautical miles, which Poling says is “wildly inconsistent” with the law.

“The rules that protected China as a developing coastal state now seem an unfair constraint on a China that believes it should be able to impose its will on its neighbors,” he said.

China’s seizure of the Scarborough Shoal has deprived Villamonte and other fishermen in the village of Cato in northern Pangasinan province of an important source of income.

Their families began fishing there in the 1980s, when larger boats allowed them to make the 500-kilometer round trip. It was teeming with fish and provided life-saving shelter during storms.

Now fishermen say they rely mostly on “payaos,” floating devices that attract yellowfin tuna that are anchored off the shoal and left alone by Chinese boats.

After decades of overfishing by neighboring countries, men have to stay at sea longer and resort to smaller fish.

Even then, they sometimes struggle to break even.

Despite the risks, Filipino fishermen are still trying to enter the shoals to stock up on their catch.

Christopher de Vera, 53, said members of his crew went in under cover of darkness and felt like “a thief in your own backyard”.

But he said the shallow waters are no longer teeming with fish after the corals were “decimated” by Chinese giant clam harvesters.

China’s growing assertiveness has not been seriously challenged by Southeast Asian countries amid deep disagreements over how to respond and fears of retaliation, analysts said.

The 10-member Association of Southeast Asian Nations (ASEAN) is divided between those with close ties to China, such as Myanmar, Cambodia and Laos, and others more suspicious of Beijing.

Their differences have hampered negotiations between China and ASEAN over a “code of conduct” that would govern behavior at sea.

The talks have dragged on for 20 years, as Beijing, which prefers to deal directly with its smaller neighbors, embarked on an island-building tour.

The United States is widely regarded as the only nation strong enough to fight back, but there are concerns about its reliability.

President Joe Biden received ASEAN leaders in May to signal Washington’s long-term commitment to the region amid China’s growing influence.

But decades of inconsistent policies and perceived neglect of the region have tarnished Washington’s image.

“Southeast Asian countries are simply not willing to bet on the United States,” said Shahriman Lockman of the Institute for Strategic and International Studies in Malaysia.

China has previously used deadly force to back up its claims, and its recent war games over Taiwan, which it considers part of its own territory, had alarm bells ringing across the region.

Chinese and Vietnamese forces engaged in clashes in 1974 and 1988, killing dozens of soldiers.

For now, Beijing seems intent on avoiding war while continuing its expansionist drive.

“They are adept at avoiding crossing that threshold by speaking shrill about their protests, that wolf-warrior diplomacy designed to intimidate you and get you to give in without a fight,” said John Blaxland, an expert on international security and Intelligence at the Australian National University.

And his tactic works.

Poling said the sea could become a “Chinese lake” as the growing risk and cost of operating there crowds out Southeast Asian fishermen, oil and gas companies and the Coast Guard.

Villamonte regularly earned 6,000 pesos (US$105) a trip if he could fish the Scarborough Shoal. Now it can be as little as 2,000 pesos or nothing at all.

Fishing is all he knows – his father and grandfather were fishermen – and his “worst nightmare” is losing access to the rest of Philippine waters.

“My family will starve,” he said.