BANGKOK — The Sentinelese, a tiny island tribe in the Indian Ocean, have a tried-and-true foreign policy.

When outsiders approach their island, they swarm the shoreline and rain down arrows.

The Sentinelese are highly mysterious. Commonly described as the “most remote” tribe on earth, they inhabit a speck of land roughly the size of Manhattan. Their population, however, is minuscule: an estimated 50 to 100 people.

Were it not for their fear of outsiders, that number might be zero. The Sentinelese are what anthropologists call “uncontacted” people. They do not communicate with the outside world. Very few people have intruded on their turf and lived to talk about it.

The Sentinelese have been derided as “savages” and “primitives” for failing to join the outside world. But their habit of killing intruders is nonetheless wise.

Modern history is filled with sad sagas of indigenous peoples eradicated or decimated by diseases borne by European visitors. As in 17th-century America, epidemics can rapidly depopulate the land and leave it vulnerable to takeover.

That has not happened to the Sentinelese. Yet.

They’ve fended off a range of characters: British colonialists, Indian anthropologists, drunk fishermen and even Jacques Cousteau.

Now the Sentinelese are threatened by a new breed of intruders: sea cucumber poachers.

According to Survival International, a London-based organization advocating tribal self-determination, fishermen are increasingly invading waters near the tribe’s island. The group suspects the seafaring poachers seek sea cucumber, a squishy little creature prized in China as a libido booster.

They’ve even heard recent reports that one poacher, a Burmese fisherman, was reckless enough to step onto the island. He was perhaps fleeing in panic from the Indian Coast Guard, which later detained the fisherman and his crew, according to Survival International, which notes that intruding fishermen generally know to keep their distance from the Sentinelese.

Some poachers have been jailed by Indian authorities awaiting trial. Many are warned and released.

Each intruder risks both his own life and Sentinelese genocide. A single handshake or sneeze could bring on mass death. “With the isolation comes extreme vulnerability,” says Sophie Grig, senior campaigner with Survival International. The Sentinelese, she says, “are likely to have no immunity to diseases like the common cold or flu.”

Contacting the Sentinelese is a criminal act. Until the 1990s, the Indian government supported attempts to contact the tribe. They were often driven away. This video reveals a rare non-hostile interaction with an Indian research crew, which did not step off their boat:

But the Indian government has stopped trying to contact the Sentinelese and instead agreed to defend their island from invasion. “Given that the Indian government changed its position ... to a policy of non-contact, we believe their isolation can be maintained,” Grig says.

Yet it appears the Sentinelese have no idea the state of India even exists. Isolated on the island for an estimated 60,000 years, they’re believed to survive off jungle pigs, honey and fruit. They have seen the wonder of flying machines — helicopters have buzzed the tribe multiple times — but the crew is always attacked with flying arrows, never cleared for landing.

The outside world is likewise clueless about Sentinelese habits and thought. Their language is unknown. Their religion, if any, is unknown. Their thoughts on love, sex, honor and the cosmos are secrets that have never left their island.

The 21st century offers new technology, drones, that allow outsiders to peer into Sentinelese life without risking a spear to the neck. But Grig says that “would be without their consent and therefore would be unethical.”

“They have made it clear that they don’t want to be contacted,” Grig says. “This must be respected.”