Touted as the largest structure ever built by living organisms, the Great Barrier Reef is the handiwork of coral polyps, some of the planet's most diminutive fabricators. Related to sea anemones, each polyp has a calcium-carbonate skeleton. Over time, they become cemented together. Arriving at our dive site, Wright fits me with a vest, tank and lead belt. The ocean resembles an expansive room with a white sand floor and a ceiling of shimmering aquamarine.
Coral walls drip in a palette of colour.
Fish provide fleeting decorations, hovering then darting off. Only breaths and bubbles break the wet silence. Suddenly, the threat of danger shatters the subsurface. I glimpse a dark, ominous shape looming in the water ahead. I've seen the TV specials.