The boat pitches up and down and rolls from side to side in the heavy swell. The noise of the big diesel motor, just below the floor, is hammering at my head.

My nose is filled with the smell of dried fish and diesel fumes, my T-shirt glued to my chest with sweat. Proper sleep is impossible.

For more than 40 hours it has been like this. Our wooden fishing boat has tossed its way across the South China Sea. Most of the time we barely exceed walking pace. “Who would be a fisherman?” I wonder out loud.

I stare out at the endless rolling waves. On the horizon the sky is dark and threatening. Then my eye is caught by something sticking up above the waves. It looks like an oil or gas-drilling platform. What on earth is it doing here?

As we get closer, to my right, I am sure I can now see something pale and sandy beside the platform. “That looks like land!” I say. It can’t be. I look at my GPS.

There is no land marked anywhere near here, only a submerged reef of the Spratly Island chain. But my eyes are not deceiving me. A few kilometres away I can now clearly see the outline of an island.

“What is this place called?” I ask our Filipino skipper.

“Gaven Reef,” he says.

“Get closer!” I shout over the din of the engine.

He turns the boat directly towards the islet. But the dark clouds are rolling in fast. Moments later we are enveloped. Water cascades off the fishing boat’s roof. The islet disappears.

“How long will the rain last?” I ask the skipper.

“Four or five hours, maybe longer,” he says.

My heart sinks. All this time, all this way, only to be beaten by the weather. But I know I have seen it, an island where there wasn’t one just a few weeks ago – even the skipper has never it seen before.

The captain turns the boat back to our old course – south, into the rain. We plough on. The waves are getting bigger. After four hours the rain begins to recede. Ahead I can see another island.

This one I am expecting. This place is called Johnson South Reef. On my GPS it again shows no land, just a submerged reef.

But I’ve seen aerial photographs of this place taken by the Philippine navy. They show the massive land reclamation work China has been doing here since January.

Millions of tonnes of rock and sand have been dredged up from the sea floor and pumped into the reef to form new land.

Along the new coastline I can see construction crews building a sea wall. There are cement-pumping trucks, cranes, large steel pipes, and the flash of welding torches.

On top of a white concrete blockhouse a soldier is standing looking back at us through binoculars.

I urge the skipper to get even closer, but a volley of flares erupts in the sky – it is a Chinese warning.