I had no expectations. If anything, I was anticipating disappointment. Not so much because of premature obituaries of the Great Barrier Reef; it was more my distrust of adjectives. I have been to enough bucket-­list tourist sites to know the experience can leave one feeling strangely empty.

I sat next to the skipper, blue water whooshing underneath us, while, on the deck below, German backpackers organised their underwater cameras and diving gear. A few of us watched the shoreline, Townsville shrinking as we got further away. Castle Hill, a mass of orange granite that separates the city centre from the urban sprawl beyond, glowed in the pink morning light. Rusted to the landscape is Clive Palmer’s Yabulu nickel refinery, its three smokestacks no longer puffing. There’s a lush strand I had walked that morning on my way to the jetty, where black cockatoos hang upside down, tearing fruit off the trees as early morning joggers dodge the leaf litter. I passed a brightly painted water playground, its movement sensors waiting for the day’s first chubby bather-­clad preschooler.

It’s often said in news reports that you can see the Great Barrier Reef, the world’s largest structure made up of living organisms, from space – as if that will convince us to protect it. But you can see a lot of things from space: China’s smog, and the “Super Pit,” a goldmine in Kalgoorlie.

In 1968, on the first human voyage to orbit the moon, the American astronaut Bill Anders was given the job of photographer. The Apollo 8 mission was focused on the moon, but then …

Anders: Oh, my God! Look at that picture over there! There’s the Earth coming up. Wow, is that pretty. Borman: Hey, don’t take that, it’s not scheduled. (joking) Anders: (laughs) You got a colour film, Jim? Hand me that roll of colour quick, would you … Lovell: Oh man, that’s great!

Anders’ words are often repeated: “We came all this way to explore the moon, and the most important thing is that we discovered the Earth.” His photo, titled Earthrise, became a lightning rod for environmentalists, who knew the blue and green swirling globe coming out of the dark was a gift too precious to lose sight of. It is a difficult task, to remember we are on a cat’s-­eye marble in a pitch-­black void.

“Are we in space?” my four-­year-­old had asked me in Melbourne, not long before I left for my reef visit.

“No,” I replied confidently, then just as quickly lost confidence. “Well, actually, we are. We are on Earth, and Earth is kind of wrapped, like a present [his eyes lit up], in our atmosphere, the sky, and all of this is in space. So we kind of are in space.”

He nodded solemnly, absorbing this before continuing with his painting, but I was trembling. It was that strange feeling of having known something for a long time, but the act of saying it out loud making it real. We are in space. I wanted to scream it on the street like a crazy woman. We are in space!

Two hundred years of science and discovery have seen a rapid reorientation of many assumptions. The first dizzying insight was that of extinction, proved by paleontologist Georges Cuvier in 1796. It had been assumed until then that life just went on. Sure, it was punctuated by death, mostly in dribs and drabs, sometimes in tragic sweeps like the Black Death, but a species did not simply cease to exist. There would always be another specimen in its mirror image, and another, and another.

It got worse. Cuvier, discovering an increasing diversity of fossils, suggested there had been catastrophes on Earth, many of them. “Life on Earth has often been disturbed by terrible events” – death en masse, in a cataclysmic blink of an eye. Then, in 1859, came the theory of evolution by natural selection. It was considered highly unflattering – we came from apes! – but survival of the fittest was also a balm to Cuvier’s catastrophes. Extinction was a by-­product of evolution, a race which humans were obviously winning. But the discoveries kept coming. As geologists scaled and studied the strata of the earth, clue upon clue began to reveal a series of rapid extinctions, in which even “fit” species had not had time to adapt. As David Raup, a paleontologist, explained in Elizabeth Kolbert’s seminal book The Sixth Extinction, the history of life on Earth consists of “long periods of boredom interrupted occasionally by panic.”

Many of these revelations are due, in large part, to the Industrial Revolution – sometimes quite literally, as in the case of Nýany, a small mining town in the Czech Republic. Here, in 1870, a diverse collection of fossils was discovered by the director of the local natural museum of history, who had gotten into the habit of splitting the lumps of coal servants delivered to his study for heating. Inside, he often found intricate traces of four-­legged creatures known as tetrapods. That he made these discoveries as he poured coal into his heater – burning the dark compressed chunks of Permian plant matter, which in turn shapeshifted again, this time into a slender length of smoke up his flue and into the sky, a culmination of atmospheric carbon that one hundred years later would initiate a sixth wave of extinctions – is a modern twist on an old parable. Cause and effect: a simple concept, but with incredibly complex effects.

*

In early 2016 the Great Barrier Reef turned white. Professor Terry Hughes, head of the multi-­institutional National Coral Bleaching Taskforce, spent eight days flying over the reef, ranking the coral from unaffected to varying levels of bleached. Sweltering inside the tiny plane, the pilot landed in a cane field so that they could remove the doors. “We left them in the field,” Hughes told me. At the same time, the taskforce had 100 researchers underwater. In the entire system – some 2300 kilometres of reefs, atolls and islands stretching from the Torres Strait in the north to Fraser Island in the south – the taskforce found that only 7 per cent of the coral had been completely spared bleaching. In the far north, it was estimated that 80 to 90 per cent of corals were either dead or dying. It usually takes a few months to recover or die from a bleaching event, but this time, in the northern part, much of the coral died instantly. It was fried. Over 65 per cent of the northern reef is dead. In a tweet, Hughes released the survey findings with a message: “I showed the results of aerial surveys of #bleaching on the #GreatBarrierReef to my students, And then we wept.”

The following week, in federal parliament, the Tasmanian Greens senator Peter Whish-­Wilson read out Hughes’ tweet and members of the Coalition laughed and gave sarcastic sighs of sympathy. Meanwhile, further north, vast swathes of green mangroves – 7000 hectares – turned a ghostly white. Off the coast of Western Australia, 100 kilometres of kelp forests were wiped out, and up in the Kimberley much of the coral bleached. Marine scientists returned a few months later and were devastated to find Scott Reef mostly dead and covered in slimy algae. Naysayers of climate change had blamed the east-­coast bleaching on an El Niño year – a natural warming cycle that occurs every five years or so – but this should have seen the west coast experience cooler temperatures. It didn’t. In Tasmania, the kelp forests along the east coast, once so giant they had to be marked on shipping maps, were pushed a little further into oblivion, while warmer water contributed to massive mortalities at the island state’s oyster farms. In Victoria an algal bloom affected up to 1700 kilometres of the Murray River, cutting off towns and farmers from water supplies. Local blooms are common, but extending for 1700 kilometres? This is the new normal.

In February 2017 the Great Barrier Reef bleached once more. Professor Terry Hughes again found himself in a small plane flying over while divers in black wetsuits flopped overboard below.

This time, the middle section of the reef was the worst affected. Welcome to the Myxocene. From the Greek word muxa, meaning “slime,” it is what Canadian marine biologist David Pauly has proposed calling the new geological epoch Earth is entering – an epoch uniquely of our own making, a sped-­up, tricked-­up version of natural warming by an excess of emissions, deforestation, overfishing and pollution.

For a time, until the late 1970s, climate scientists were unable to say with certainty if human-­made emissions were going to cause the planet to cool or warm (their formidable task was complicated further by the effect of aerosols on the atmosphere). Today, however, the evidence is unequivocal. Coral reefs are one such indicator. Occurring, with the odd exception, within a band of water from the Tropic of Cancer to the Tropic of Capricorn, these reefs form a ring around the globe. Since the 1980s they have been taking direct hits.

Bleaching was first noted in 1911 at Bird Key Reef in Florida Keys. Since then there has been the odd minor instance, but en masse is a recent phenomenon. It is an irony of sorts that just two years after the Great Barrier Reef was accorded World Heritage status in 1981 – rescuing it from being mined for cheap limestone fertiliser and drilled for oil – the first mass bleaching occurred: this is not a threat that can be controlled by declaring a zone protected.

Global warming is pushing up temperatures in the ocean at a rate too fast for most corals, and all that rely on them, to adapt. An unseen side effect of this temperature rise is a change in chemistry. Carbon and methane emissions are making the sea acidic. A warming and increasingly acidic ocean will see a cascade of effects, such as more algal blooms; the demise of crustaceans, as their shells become too brittle and difficult to form; and coral reefs turning to rubble, taking with them the livelihoods and sustenance of 500 million people worldwide.

The Myxocene is not in the future; it is already here. In the coastal waters of Japan since the 2000s, plague-­like blooms of jellyfish have overwhelmed fishermen, with 500 million or so blotting otherwise empty ocean. Fishing boats began to attach wire grills to the ends of their nets, metal teeth slicing the mass of globs into pieces. It was a bad idea – the gelatinous mincing dispersed billions of eggs from the female jellyfish.

In 2013, in the Pacific Ocean, a bewildering “blob” of warm water parked itself for two years, clinging to North America’s west coast. A highly toxic and long-­lasting algal bloom saw thousands of sea lions and seabirds, as well as hundreds of otters and whales, suffering seizures and dying, shutting down shellfish farms and other fisheries.

It is expected that weird bodies of mucus in the ocean, known as “dead zones,” some over 200 kilometres long, will become more common. In 1991 an Italian marine biologist, Serena Fonda Umani, swam alongside a “mucilage” in the Adriatic Sea. A National Geographic article in 2009 described the mass as “too dense to swim inside.” The article continued: “She remembers diving about 50 feet (15 meters) down when she got the sensation of a ghost floating over her—‘sort of an alien experience.’”

There are people who say this has happened before, often arguing in the same breath that action on climate change is therefore foolish. They are right on the first count. In Precambrian times, before fish evolved, oceans were slimy and hot. As for their conclusion – that nothing need be done to curb emissions – so far, no scientist has discovered evidence of thriving human communities living alongside such oceans.

*

“Like most Australians,” Kate Jennings wrote in her essay “An Otter’s Life,” “I am a swimmer.” It was with this one line that I wrestled down doubt about visiting the reef, the feeling there was something gross about my going to see it. I had, after all, felt a hot rage when I saw the Australian this year promote its travel supplement with the headline “Endangered Destinations: The things to see before they disappear” – yet here I was, packing my bag. It felt naive too, not so dissimilar from a recent visit to the reef by Pauline Hanson, who flopped into the water in her kit and declared to cameras that the reef is “pristine.” What would she know? What would I know? But now, on the boat, passing Magnetic Island, these Melbourne hang-­ups were blown away with the wind. It was Sunday. My phone had no reception. Someone was looking after the kids. The boat could stop right here, in the deep blue, plonk me out like a sinker and I’d be content.

Then I saw it. I stood up fast, my arm flung out, pointing. “Is that it?” The skipper nodded. Ahead of us, deep dark water had suddenly transformed into rippling vast strips of turquoise, eggshell blue, a strange luminous green. I felt my chest leap with excitement. Everyone else was below, already dressed in their gear and lining up to fall into the water. I hurried to the ladder and practically slid down to join them. As I did, a flush of electric-blue fish skittered out of the water beside the boat in an arc. I found my snorkel and mask, pulling on the daggy blue stinger suit as the boat’s crew leader buddied us up. I was with a girl called Grace, a James Cook University student. We smiled at each other, and then we were in.

In the water, I dived down and closed my eyes, giving my body a twist and roll up to the surface, a little ritual. There was a crackling sound, like the Magic Gum my brothers and I used to buy at the milk bar, a sachet of popping candy you poured onto your tongue, where it fizzed and crackled. Fanned out below was the strangest world of corals, some pulsing as if soft, others brittle, the colours an unexpected autumnal palette of mustard yellow, velvet red, tan suede and brown corduroy. Others pulsed fluorescent purple nipples and tubes of glowing pinks, patterns as intricate as the map of a subway, thousands of tiny tongue-­pink tips waving, breathing, and long lumpy sea cucumbers with zebra stripes. In between atolls on a pocket of sand lay a solitary stingray, and the frilly mouths of enormous clams flinched when you wiggled your fingers near them, fluorescent green squiggles glowing and you could see right inside their pearly innards.

“How big were they, Mum?” my four-­year-­old asked on the phone that evening.

“The clams?”

“Yes!”

“Some were as big as our bathtub, others as big as our kitchen chairs.”

“The new kitchen chairs or the old ones?”

“Um, the old ones.”

“Wow.”

*

Two hours later, on the boat for lunch, the crew leader commended everyone for staying close by, “except for Anna and Grace.” With as much sternness as you’re allowed to muster towards paying customers, he looked at us: “Were you two just going to keep heading out to sea?” Maybe. At the beginning, we looked up every now and then to check our distance from the boat, but then swam as if in a dream. Now, as we ate sandwiches, the crew leader spoke about the reef. He told us about the crown-­of-­thorns starfish: native to the reef, it has a voracious appetite, expelling its stomach out of its mouth and over the coral, eating the equivalent of its body mass in one sitting. Forty years ago, populations of the crown-­of-­thorns starfish began to explode. One of its natural predators, the giant triton, had been extensively collected for its ornamental shell and this was thought to be the cause, but by the ’70s it became clear the starfish were also thriving in the nitrogen-­rich run-­off (mostly fertiliser from sugarcane and banana farms) into the reef’s catchments. “They hide under the corals during the day,” the crew leader told us, “and come out to eat at night.”

After lunch, Grace and I swam out again. There was a single coral that looked like an enormous brain, as big as a VW Beetle. As if my eye was now trained, I saw a crown-­of-­thorns starfish on top of another coral, busy chomping away, too hungry to wait for night. I tried to dive closer, snorkel in hand, but my ears couldn’t take the depth. Grace and I dipped into a small cavern and found ourselves inside a shoal of thousands of electric-­blue fish. They shivered around us, then up came a second shoal of slightly bigger turquoise fish and a third shoal of larger green fish with pink threaded scales.

We floated in a trance.

I found that when I waved my hand through the water, the small electric-­blue fish would swing away, triggering the next shoal to shift, and so on. I started to move my body like a conductor, using tiny movements to press against and shimmer the shoals, bringing them back, then away, rounding in on them, and pausing so that they would flood back up from the depths. At first we didn’t notice the corals getting closer to the surface, the tide going out, inching towards our flippers. Then we heard the boat sound its horn. Grace and I had been in the fish shoals for nearly two hours. We looked at each other, put our heads down and pretended not to hear the blast. I started to swim the other way and the horn blasted again. I saw Grace turn reluctantly and swim in. I kept going.

“One more minute,” we used to scream to our parents beckoning from the beach as waves curved behind us, lifting our tiny bodies into the air before throwing us down, pushing us deep until the air left our chests and then letting us go – when we would wriggle and kick up to the surface, hair tossed like seaweed, bathers at times in a tangle around our ankles, and we would scream, again, “One more minute!” I heard the horn blast a third time and I knew this time it was just for me. One more minute, I thought, and dived deep, scanning, trying to swallow it all with my eyes: the coral, the chunky fish with knobbled brows, the crackling sound I imagined was the invisible machinery of crustaceans. There was the absence, too, for I’d felt it, despite my lack of expertise. There’d been turns, spooky corners where Grace and I ought to have come face-­to-­face with a creature, an unnerving marine intelligence, but there’d been nothing. I swam to the lip of the boat and took off my mask and snorkel, leaving it on the metal shelf and went under one more time. A little ritual.