An Ode to Life at Richelieu Rock

Evolutionary dispatches from a hidden world, as I explore one of the most fascinating underwater sites on the planet.

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A hundred feet below the surface of the emerald waves of the Andaman Sea, I’m encased in an eerie stillness, rhythmically pierced only by the hiss of my inhales and the slow, relaxed exhales that follow. Twenty-eight miles off the coastal border of Thailand and Myanmar, the relentless cacophony of life on land has disappeared. But there is another, quieter world lurking below.

Weightless, silent, suspended in crystal clear waters, I’m still in a state of sensory overload. The horseshoe-shaped reef beside me pulses with life, as seething currents drag nutrients from the darker blue emptiness beyond, and nutrients attract the hungry.

There is movement everywhere, as thousands upon thousands of tropical fish cascade in unison, their shoals seeming to wash over rugged cliffs of limestone and purple coral. Explosions of vibrant color flash around me. A green-tinted eel opens and closes its mouth, baring its jagged teeth as I swim past, gazing out from a crevice in the rock. Countless bluestreak cleaner wrasse flit past, signalling their readiness to dutifully eat parasites that cling to any passing sharks, silvery barracuda, or fluttering manta rays. A cornetfish inspects me, a stranger-than-fiction species that looks as though a clown grabbed it and stretched it like a balloon animal, mostly for comic effect.

Wherever I look, there is a chaotic storm of improbable creatures. These are the culminations of billions of years of evolutionary tinkering, the greatest trial-and-error experiment ever undertaken, stretching from single-celled organisms, blossoming to the majestic complexity of what Charles Darwin called “endless forms most beautiful.” And those endless, beautiful forms have lessons to teach us, if only we have the wisdom to learn from them.¹

I: The Sea Casts a Spell

A few weeks ago, I ventured back to Thailand—one of the countries I study for my research. Normally, I’m there to study corrupt, authoritarian politicians, interview stony-faced generals, and decipher why it’s the most coup-prone country on the planet. But this time, I also had a different purpose: ticking a longstanding item off my bucket list, a liveaboard SCUBA adventure, 14 dives crammed into four exhausting but unforgettable days exploring an unfamiliar world.

Descending into the depths of the ocean is, for most of us, the closest attainable experience to venturing onto another planet. Once you get beyond the initial bewilderment of your first time SCUBA diving—the heightened sense that you’re very much like a fish out of water, or more accurately, a human underwater—there begins a euphoric, but calming sensation of otherworldly transcendence. “This was here all along,” you think to yourself, as the teeming beauty of that liquid world was utterly invisible as I lived my life above the surface. “And it is completely unlike anything I’ve ever seen.”

Humans, for our entire existence, have tried to venture beneath the waves. Mummified human remains from seven thousand years ago in Chile show signs of prolonged exposure to cold water diving, likely for mussels and limpets, the evidence of undersea pressure etched into telltale signs around their ear bones.

But no matter how much we may be fascinated by the world below, we have been constrained, evolutionary prisoners of our landlubbing lungs. As Tim Ecott chronicles in his book Neutral Buoyancy, clever people throughout history have long tried to overcome those limitations with fresh technology, dating back to at least the 4th century BCE.

Aristotle claimed that an early incarnation of this impulse was to lower air-filled cauldrons (lebes), allowing a diver searching for sponges to stick their head inside while underwater, gulp some air, and continue their search. Less convincing accounts suggest that Alexander the Great descended to the ocean floor in a glass barrel, but as Ecott notes, this seems somewhat less credible given that the story appears alongside reports that an enormous sea monster was observed, so large that it took three full days to pass by.

After much experimentation—with moderate success—using diving bells, particularly from the 1500s onward, it became obvious that underwater activity would be much easier if the air supply could be tightly encased around a human head. Primitive but functioning diving helmets emerged as early as the 1770s, but these were prone to disaster and limited to shallow depths.

Such limitations were partly due to the properties of atmospheric pressure in water. At sea level, there is one atmosphere of pressure. As you increase elevation, the atmospheric pressure thins, but slowly; there is about one third as much atmospheric pressure on top of Mount Everest compared to sea level.

But in water, which weighs far more than air, pressure shifts much faster, increasing by one full atmosphere every 33.8 feet of depth. That means that modern recreational divers who descend to 100 feet are experiencing pressure akin to four atmospheres worth of pressure, compared to just one on the surface. Without the right mechanisms and care to account for these enormous shifts in the gases inside of us, or diving with the wrong kind of air supply, or surfacing too quickly, can each quickly prove fatal.

In the late nineteenth century, the Scottish scientist and philosopher J.S. Haldane set out to explore the properties of gases in human bodies, driven by a desire to understand why mines so often proved toxic to workers. Guided by his personal mantra of “why think when you can experiment?” Haldane made himself a guinea pig. He routinely locked himself inside airtight chambers with various noxious and potentially lethal gases, simply to observe the unusual effects on his body.

One night, after rather thoroughly gassing himself, Haldane stumbled through the streets of Oxford, and was stopped by a passing policeman. He assured the officer that he had been deliberately exposed to toxic gas, not to alcohol, and was let off to stagger home. Haldane’s housekeeper, when told of the incident, offered her sympathies to Haldane’s wife, Kathleen. “I know how you feel, ma'am,” she said. “My husband's just the same on a Friday night.”²

Haldane’s research paved the way for decompression tables, scientific guidelines of how to properly manage nitrogen levels and descend into ocean depths without dying. Armed with that knowledge and a series of scientific breakthroughs—furthered by the desire to use diving warriors such as frogmen in World War II— recreational diving soon became plausible, eventually popularized by Jacques Cousteau and his groundbreaking Aqualung.

With dazzling photographs of what lurked below, Cousteau helped make SCUBA diving a sport. With it, we became one of the few species that could reliably produce its own artificial air supply for the underwater world, following in the footsteps of Costa Rica’s Anolis lizards, who produce an air bubble above their noses, a reptilian proto-SCUBA tank that allows them to stay underwater for twenty minutes.

Now, seventy years after Cousteau began to showcase the hidden mysteries of the ocean, PADI, the main diving certification body, has trained thirty million people to SCUBA dive, bringing a measurable but nonetheless tiny slice of our species into this bewitching realm.

For those lucky few, as Cousteau later observed: “the sea, once it casts its spell, holds one in its net of wonder forever.”

II: Encountering Alien Life at Richelieu Rock

At 5:45am, the boat awakens to the sound of jingle bells, a makeshift alarm clock to rouse groggy divers from their cabin bunk beds. Roaming through the cabins with the bells is Vince, a stoic and burly highly accomplished Scottish professional diver who occasionally moonlights for the Thai navy to recover undersea bodies whenever a fishing boat or ferry sinks.

“With their religious beliefs and superstitions, they don’t like to do that work, so I do it for them,” he tells me. Vince has been in Thailand for decades—so long that he’s lost count of how many dives he’s done, but the number is surely in the tens of thousands. He’s as close to a fish as a human can get.

This morning, after two days of diving near the tiny Similan Islands, which dot the open ocean as the only land within thirty miles, it’s time to explore Richelieu Rock. Blink and you’d miss it, as it’s an undersea limestone pinnacle that soars from the seabed 115 feet down, but only slightly breaks the surface of the waves.

The site is named after Admiral Richelieu, a Danish marine captain, who moved to Thailand in the late 19th century, met the king, and charmed him—partly because he was the same height, which mattered greatly in royal customs of the time. Richelieu was soon made admiral of the Thai navy and discovered, by accident, the tiny outcropping of limestone in the middle of nowhere, oblivious to the teeming life that lurked below.

After the jingle bells have roused us, twenty-two of my fellow divers groggily emerge to don their wetsuits—including a retired zoo director, a bigwig California cannabis entrepreneur, an Australian ecologist, and a construction worker. We sip coffee, then descend to the dive deck at the back of the boat. One by one, we strap ourselves into our buoyancy jackets, open our Nitrox tanks filled with 32% oxygen rather than the 21% found in surface air, and tighten our weight belts. Then, we waddle in our flippers—a spectacle of comic awkwardness as we transform into unnatural sea creature burdened by the weight of our tanks that accompanies above sea gravity—to clamber into cramped black dinghies.

The motor whirs as we shoot off across the glassy ocean, our faces bathed in the most spectacular soft pink and orange flickers of sunrise, reflected off the shimmering water. When we arrive at the pinnacle, we count to three, then barrel roll backwards into the waves. With a thumbs up, we empty the air in our buoyancy vests, then slip into an alien world.

It’s still dark underwater as the sun’s first rays crack the horizon, so we use our flashlights as we explore a hundred feet down. Illuminated within the beams of light are bannerfish, malabar groupers, and the occasional spiky oddities of porcupinefish and lionfish. The whirlwind of life is equal parts fascinating and overwhelming; it triggers a profound sense of awe, a powerful feeling of individual insignificance within this vast blue-green expanse. But as thousand-strong schools of fish dart around me, hunting or avoiding being hunted, there’s an even stronger thrill, as I spot one of the most interesting creatures on the planet—one that I have, for years, longed to see in the wild.

Scuttling out from its hiding place in the purple corals and grey limestone on the seabed is a peacock mantis shrimp, one of the most beguiling byproducts of evolution in existence. Literary descriptions can’t do this amazing animal justice, but I shall be foolhardy and attempt one nonetheless.

Its shell is a psychedelic kaleidoscope of color, with a glimmering blue, green, and orange lobster-style back converging toward its head, which is adorned with bug-eyed baby blue eyes perched atop a stumpy stalk. Appendages sprout out of its head in a whimsical, downward drooping swoop, like the crustacean version of a Fu Manchu moustache. Its underbelly is a bright, fluorescent shock of red.

Flamboyant appearances aside, this little stomatopod packs the most powerful punch in the world, its club striking with a speed 50 times faster than the blink of an eye, and with a force 1,000 times its body weight. The impact is so great that it produces a shockwave by unleashing vapor-filled bubbles, which stuns the unfortunate victim, doubling the effect of the blow.³

In an effect known as cavitation, the club’s velocity causes the water around the mantis shrimp’s weapon to briefly vaporize, temporarily reaching 8,500 degrees Fahrenheit, nearly the same temperature as the surface of the sun. The club can split human thumbs and break aquarium glass. (I politely failed to provoke it, eager not to test these extraordinary aptitudes firsthand).

And yet, the peacock mantis shrimp’s unrivalled punch is the second most interesting feature of these psychedelic creatures. Their color perception vision is truly otherworldly—and remains stubbornly beyond human understanding.

With three types of photoreceptors in our eyes (red, green, and blue), humans are trichromats. Dolphins and whales are monochromats, navigating the oceans in black and white. Most non-human mammals—including our beloved dogs—are dichromats, so they see the world a bit more like a human who is red-green colorblind. Most birds, fish, reptiles (and probably dinosaurs) have four kinds of photoreceptors, allowing them to see ultraviolet light, so they’re tetrachromats.

Rather than one, two, three, or four photoreceptors, the peacock mantis shrimp has sixteen, a number with no parallel in the animal kingdom.

Evolution’s wisdom lies in the trial-and-error approach embedded in its ever-experimenting genomic mechanisms. And yet, even though such experimentation has created the most ingenious solutions to facilitate survival in changing and often harsh environments, there need not always be a “just so” explanation for why a trait has emerged. As with human history or social change, life forms can sometimes be the byproduct of the arbitrary or the accidental, the evolutionary contingencies and “what ifs” that perplex us. Perhaps the peacock mantis shrimp’s vision is one such peculiar oddity, a living fluke of nature.

As this particular peacock mantis shrimp frantically scampered across the sand, I saw its eye stalks slightly turn to examine me. I couldn’t help wondering: what did I look like to this astounding being, with vision that can only be imagined by our comparatively puny senses? Would that peacock mantis shrimp pity me if it had the cognitive capacity to do so, trapped as I was in a comparatively dull realm of limited perception, while evolution’s mysteries had conferred upon it unique access to a far more vibrant world?

III: Cleaning Stations and Oceanic Game Theory

As the mantis shrimp returned to its crevice, I propelled myself forward with my fins, getting closer to various limestone outcrops that might serve as cleaning stations—astonishing sites of symbiotic economic exchange on coral reefs.

The terms of nature’s win-win deal at cleaning stations are straightforward: a large fish, such as a manta ray or a whale shark swoops in, covered in harmful parasites that have stubbornly affixed themselves to its sprawling body. Since evolution has declined to give these fish proper hands or limbs, it is impossible for them to rid themselves of these meddlesome parasites. Fortunately, smaller fish, most commonly species like the bluestreak cleaner wrasse, are happy to provide a parasite removal service, as each parasite provides a nutritious meal.⁴

Game theory provides an economic framework for understanding repeated interactions, in realms above and below water. If you go to get your car serviced and the shady mechanics cut corners, overcharge you, or fail to fix the problem, you’re likely to go elsewhere the next time around. Repeated interactions in a fixed geographic space—such as your local community—therefore increase the rewards for honest dealing and the penalties for cheating, particularly when it’s easy to share information about whether the mechanic was correct or crooked.

The same mechanisms govern undersea reef cleaning stations. The interactions are based on high-stakes trust. In some instances, tiny cleaner fish must make themselves completely vulnerable to being eaten, entering the mouths of apex predators to clean parasites off their carnivorous mouths. When it works as intended, the cleaner gets a meal and the bigger fish gets some long overdue health care—a form of reciprocal altruism. Cleaner wrasse may engage with clients and prospective clients as many as 2,300 times per day.

Safe interactions for both parties rely on signalling theory, in which species communicate their intent, ideally through honest signals. For the bluestreak cleaner wrasse, lab “experiments have determined that their colouration of vibrant blue stripes bisected by a pronounced dark lateral line is universally recognised by other fish instinctively, as a cleaner.” Evolution, it turns out, has developed an easily recognized janitor’s uniform.

However, as on land, there can be upsides to dishonest behavior underwater. Cleaner fish would prefer to swap out some of the parasites they eat for a richer meal of tissue, scales, and mucus from the larger fish. To get such tasty treats, however, they must nip the larger fish, which produces pain—a violation of the implicit bargain of the parasitic cleaning process. When the nips happen, all the nearby cleaner fish lose out because the larger fish swims away, and may not return for a future clean. There are other more honest services available, after all.

But as with humans—where there’s significant evidence that “watched people are nice people”—cleaner wrasse behave better when they’re being observed by their fellow fish. If a female cleaner wrasse nips a client fish, the male will “punish” her by chasing her away from the cleaning station. After that happens, she is more likely to follow the rules of the economic exchange, only eating parasites and giving both fish a better chance at a full meal. It’s an enforcement mechanism that, through evolutionary pressures, allows tiny fish to safely swim inside the mouths of predators that would otherwise devour them without a second thought.

Astonishingly, large client fish—rays and sharks, for example—can even remember the crooked cleaners who violate nature’s “win-win” deal. They may not return to individuals who nipped them in previous interactions, or will avoid entire cleaning stations if they got bad service in the past. This enforcement protocol breaks down, however, if large fish only irregularly frequent cleaning stations. Without repeated interactions—and lacking a fish version of Yelp or TripAdvisor—some fish may unknowingly drift into cleaning stations that the more tuned-in reef locals have learned to avoid.

However, evolution can also unequivocally reward clever deviousness, as evidenced by the diabolical corruption of the bluestriped imposter fangblenny. This extraordinary fish can change its colors at will, donning a disguise before it commits its crimes on the reef.

Normally, as Ed Yong notes, the fangblenny looks “brown, olive or orange with white or light-blue/green stripes.” But when it approaches a cleaning station and a prospective client of the cleaner wrasse, the fangblenny switches to sporting “a black body and an electric blue stripe that mimics the wrasse.” By fooling the client, it can safely approach a deadly predator, painfully nibble off a bit of mucus or scales, then dart away unharmed. The natural world, like human societies, sometimes rewards those who play by the rules, and sometimes, those who don’t.

Unfortunately, whether out of bad luck or due to a particularly crooked set of nearby cleaners, there were no manta rays swooping in to be cleaned while I swam amidst the bluestreak wrasses. However, a few hours later, my luck turned around: I found myself swimming alongside three rather fearsome but majestic prospective future clients of cleaning stations: a trio of blacktip reef sharks.

IV: On Swimming with Sharks and Feeling Alive

Florida’s New Smyrna Beach is the shark attack capital of the world, with over 300 recorded incidents of shark bites. None of them, however, have been fatal, and that’s because the majority have been carried out by blacktip reef sharks, a less lethal shallow sea dweller that occasionally nibbles on humans, typically in cases of mistaken identity.

Sharks are living fossils of bygone eras, having emerged more than 400 million years ago. Ancient species have been recognizably similar to modern sharks for nearly as long. Sharks are extraordinarily resilient, too, having survived five mass extinction events that wiped out vast swaths of less adaptable species.

When a shark swims nearby, as I would soon find out, the initial twinge of instinctive fear quickly gives way to awe, the sensation of being in the presence of a truly extraordinary creature—one that’s likely to roam the oceans long beyond the moment that humanity is snuffed out.

It’s late afternoon, our final dive of the day, in a shallow reef just off the coast of the Surin Islands. After the flurry of life at Richelieu Rock, I’m enjoying a bit of weightless floating in a quieter, more tranquil bay. Suddenly, our bubbly Spanish divemaster, Yolanda, abruptly shoots her arm out, pointing off into the murky distance. My eyes light up at the sight of a sea turtle gliding ahead, but then I see what she was actually pointing at: a five foot long blacktip reef shark, patrolling through enormous undersea boulders in the shallow waters of the reef.

Curiosity instantly triumphs over fear, so I kick my flippers hard and follow its patrol. But I’m no match for its perfectly evolved swimming speed, and the shark is understandably more afraid and less curious about me, so it soon disappears into the dappled blue waters ahead.⁵ Two more blacktips soon come into view, then fade away into the distance, providing brief but spellbinding encounters.

Twenty minutes later, we surface, bobbing together on the choppy waves. I spit the regulator out, take a breath of warm, uncompressed tropical air, and my face involuntarily breaks into a wide smile. My entire being is gripped by an overwhelming exhilaration, a pure distillation of the joy of being alive.

That euphoric feeling is coming not from heart-racing fear, but from the transfixing wonder of glimpsing the defining—but mostly hidden—underwater landscape of our endlessly beguiling planet. We all exist, mostly oblivious to a vast alien world, even as it’s packed to the gills with an evolutionary menagerie of astonishing cohabitants. And, for a fleeting time, I was fortunate enough to jettison the bonds of gravity and air, to enter their vast, wondrous dominion.

“How inappropriate to call this planet Earth,” Arthur C. Clarke once correctly observed, “when it is clearly Ocean.”

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Happy but tired, on the dive boat.

1. With the exception of the peacock mantis shrimp photo, I shot the videos for this essay.

2. Haldane also experimented on his son, J.B.S. Haldane, who later took up the family pastime with enthusiasm. The younger Haldane once gave himself such violent seizures during these self-experiments that he crushed his own vertebrae. Writing about the effects of perforating an eardrum in his own experimental pressure chamber, J.B.S. showed his glass-half-full personality with one of the best quips in scientific history: “The drum generally heals up; and if a hole remains in it, although one is somewhat deaf, one can blow tobacco smoke out of the ear in question, which is a social accomplishment.”

3. Recent research into the ingenious, tough material structure of the mantis shrimp’s club is already being used to strengthen everything from hockey sticks to airplane wings and wind turbine blades.

4. Cleaner wrasse are one of the few fish species to demonstrably pass the “mirror test,” in which they are self-aware enough to recognize themselves in a mirror.

5. Humans kill an estimated 70 million to 100 million sharks per year, mainly through commercial fishing. Five to ten humans get killed by sharks most years, and about half of those attacks are provoked. It’s pretty clear which species should be feared.