The winch halted. Rajendra looked up, back toward Stateless, tilting the lantern on its pivot, swinging it back and forth.

Milky water roiled in a layer that clung to the underside. Fine particles of limestone? I was confused; why didn’t they simply fall? Even from strobed stills, I could see that this haze was in constant motion, surging rhythmically toward the hidden rock. I could also make out bubbles of gas, dragged down a few meters in some kind of undertow, before finally escaping back into the haze. Rajendra played the beam back and forth, improving his control; the lantern was obviously difficult to manipulate accurately, and I could sense his frustration – but after a few minutes his persistence paid off.

A stronger-than-average surge mixed an updraft of clear water into the milky layer above, parting the curtain for an instant. Beam and camera transfixed the event, exposing lumpy rock sparsely populated with barnacles and pale, frond-mouthed anemones. In the next frame, the image was blurred – not yet obscured by the haze of white particles, but crinkled, distorted by refraction. At first, we’d seen the rock through pure water; now we saw it through water and air.

There was a thin layer of air constantly trapped against the underside, maintained by the steady stream of oxygen escaping from the foamed rock.

This air gave the water a surface which could carry waves. Every wave which crashed on the distant reefs would send a twin diving beneath the island.

No wonder the water was cloudy. The underside of Stateless was being constantly scraped by a vast, wet, jagged file. Waves eroded the shoreline – but at least that stopped at the high-tide mark. This assault was going on beneath dry land, all the way to the rim of the guyot.

I turned again to the woman beside me, one of Rajendra’s friends. “The limestone detritus – tiny particles like that must lose all their oxygen, all their buoyancy. Why don’t they just … fall?”

“They do. The white comes from engineered diatoms. They scavenge calcium from the water, mineralize it – then migrate up and paste themselves into the rock when the waves dash them against it. Coral polyps can’t grow in the darkness, so the diatoms are the only repair mechanism.” She smiled, hyperlucid; she’d been there to see for herself. “That’s what holds the island up: just a fine mist of calcium, fading away into the depths, and a few trillion microscopic creatures whose genes tell them what to do with it.”

The winch started rewinding. No one was near it; there must have been a control button for the diver, which I’d missed – or maybe it was preprogrammed, the whole dive calculated in advance to limit the risk of decompression sickness. Rajendra put his hand in front of his face and waved to us. People laughed and joked as he began his ascent; it was nothing like the mood when I’d arrived.