The truck moved between two broad streams of crushed coral. In the distance, other streams widened and merged, the fingers of reef-rock between them narrowing then vanishing, until the land around us was more than half sludge. The part-digested coral grew coarser, the surface of the channels less even; glistening pools of water began to appear. I noticed occasional streaks of color surviving within the bleached limestone – not the muted trace minerals of the city’s masonry, but vivid, startling reds and oranges, greens and blues. The truck already stank of the ocean, but soon the breeze – which had been carrying the scent away – began to compound it.

Within minutes, the landscape was transformed. Vast banks of living coral, inundated with ocean water, surrounded narrow, winding causeways. The reefs were dazzling, polychromatic; the algal symbionts living within the various species of coral-building polyps employed a rainbow of distinct photosynthetic pigments – and even from a distance I could make out wild variations of morphology between the mineralized skeletons of each colony: pebbled aggregates, riots of thick branched tubing, delicate fernlike structures – no doubt a pragmatic exercise in diversity for the sake of ecological robustness, as well as a deliberately opulent display of bioengineering virtuosity.

The truck stopped, and everyone else clambered off – except for the two people I’d seen shifting crates onto a freight tram back at the terminus. I hesitated, then followed the crowd; I had further to go, but I didn’t want to attract attention.

The truck moved on. Most of the other passengers were carrying masks, snorkels, flippers; I wasn’t sure if they were tourists or locals, but they all headed straight for the reefs. I wandered along with them, and stood for a while, watching, as they stepped gingerly out onto the half-protruding coral, heading for deeper water. Then I turned and strolled north along the shoreline, away from the divers.

I caught my first glimpse of the open ocean, still hundreds of meters ahead. There were a dozen small boats moored in the harbor – one of the six armpits of the giant starfish. The view from the air came back to me, fragile and exotic. What exactly was I standing on? An artificial island? An ocean-going machine? A bioengineered sea monster? The distinctions blurred into meaninglessness.

I caught up with the truck at the harbor; the two workers loading it glanced at me curiously, but didn’t ask what I was doing here. My idleness made me feel like a trespasser; everyone else in sight was shifting crates or sorting seafood. There was machinery, but most of it was very low-tech: electric forklifts, but no giant cranes, no vast conveyor belts feeding processing plants; the reef-rock was probably too soft to support anything heavy. They could have built a floating platform out on the harbor to take the weight of a crane, but apparently no one felt it was worth the investment. Or maybe the farmers simply preferred it this way.