HERE in the middle of nowhere, mobile phones inside small plastic bags festoon the rusting steel girdles of a crumbling watchtower that sways with the lightest breeze.
It is the digital-age spin to the message in a bottle. Placing their phones high up on the tower to pick up signals is how the inhabitants of the island of Thitu get their text messages and stay in touch with the rest of the world.
Lying 480km west of the nearest land mass, Palawan province, Thitu is the most isolated village in the Philippines.
It is also in the middle of one of the most disputed areas on earth.
Thitu, at 37ha, is the second largest isle in the Spratlys, a chain of islands, shoals, reefs and rocky outcrops in the South China Sea to which several countries have overlapping claims, including the Philippines and China.
The Philippines has outposts on nine reefs but, apart from Thitu, those consist of just scrappy groups of a few men and some wood and iron meant to declare to interlopers: We are already here. Do not trespass.
Thitu, occupied by the Philippines since 1970, embodies Manila's claims in the South China Sea. If it is lost, the claims will be reduced to bluster on paper before some international court.
Already, for its inhabitants, Thitu feels as if it is under siege.
"(The Chinese) are getting closer," Major Ferdinand Atos, commander of a small contingent of Philippine soldiers on Thitu, told journalists on a reporting trip there on May 11 organised by the Philippine military.
Last year, rumours swirled that China has drawn up plans to invade Thitu. That turned out to be just think-tank hokum.
But since then, China has been building, with surprising speed, massive artificial islands on all seven reefs it occupies in the Spratlys. One of these reefs, Subi, is just 24km from Thitu.
In a matter of 10 weeks from February this year, China has added to Subi a more-than-4km stretch of land, long enough for an airstrip. A chain of cranes, dredgers and buildings ringed by Coast Guard ships can be seen in Subi from Thitu.
Since last month, China's warships have been driving away Philippine planes flying over Subi, telling them by radio that they are flying in restricted airspace.
"It's turning into a no-fly zone," said Maj Atos.
That worries everyone on Thitu. Planes circling to land on the island have to fly over Subi. If that airspace is shut or severely restricted, there will be no other way to resupply Thitu's nearly 100 inhabitants and their sentry. Thitu lacks a pier or harbour that can take in cargo vessels.
Most of the island's residents can get their own food by fishing, but they rely on airlifts for almost everything else: drinking water, clothing, soap, toothpaste, repair kits for their houses, top-ups for their cellphones. They have only four nurses and no doctor. The only way to evacuate someone who has fallen seriously ill is by plane.
It was in 1978 that civilians were first brought to the island to help the soldiers maintain and repair facilities. In 2002, whole families were allowed, to encourage the workers to stay longer.
Most of the civilians work in construction. They help maintain the runway and the few buildings, including a primary school. There are also utility personnel who keep the power and taps running, teachers and village councilmen.
Thitu's hardy settlers say they are ready to fight, but they harbour no illusion that they will be able to put up any credible resistance once China decides to move in or supplies dry up. Most of them are ready to leave at a moment's notice.
"We are always ready. Our things are in plastic containers that we can easily take with us," said Ms Rovelyn Jugo, 22, whose husband is a construction worker in Thitu. The couple have been on the island since 2010.
For Mr Ronnie Cojamco, 40, an odd-job worker, Thitu is home.
He does not see himself living anywhere else, but he too is ready to leave if left with little choice.
"It will be painful," said Mr Cojamco, who has the dark skin of a man who has spent too much time under the sun and the weary look of someone who has been asked too many times the question: Why are you still here?
"By reason, we have the right to be here. We have already given up so much."
Living on Thitu has meant great personal sacrifice for everyone on the island.
A day or two in this frontierland can be enchanting. White beaches ring this palm-studded, tadpole-shaped island.
At high noon, only the sound of the sea gently slapping the shoreline and the wind whistling softly break the silence. Turquoise waters spread out in all directions for what seems like infinity.
Living on the island, however, requires the constitution of men who believe they are islands.
Thitu is nearly off the grid. There is no Internet and news comes from spotty satellite feeds on TV. The 29 children here have seen shows on Cartoon Network, Disney Channel and HBO, but they do not really know the world outside their island.
There are no cars on Thitu. It takes less than 30 minutes to walk from one end of the island to the other. There are no malls, or any of the accoutrements of modern city life. There is electricity for just five hours a day.
As a garrison, Thitu has a 1.2km airstrip. A plane lands there to bring supplies and fresh troops once every two months.
From its highest point 3m above sea level, Thitu offers a breathtaking view. But it is the same view day after day. After a week, it becomes banal. After a month, it is depressing.
Mr Cojamco has been looking at that view since 1999. He remembers telling himself as he watched the boat that took him to Thitu sail away: "Why, of the many places in this world, did you end up here?" But he is a man with the constitution of an island.
He says he believes he is meant to live and die on Thitu.