Connoisseurs´ guide

to Cocos

Oct 2001, by Simon Rogerson and Douglas David Seifert
© copyright by Undersea Hunter Group
Simon Rogerson diving in Coco Island in 2010.
For more than three centuries, wherever and whenever storytellers gather to relay the tales and legends of the sea, one constant theme reprises itself time and time again. The theme is of an island, unique throughout all the islands of the world. An island small and remote, set far away in the shark-infested waters of the Pacific Ocean. An island mountainous, rich with waterfalls and fresh water, covered in dense tropical foliage rising above the rocky cliffs of its forbidding shore. An island where pirates have buried their great treasure hordes, treasures of inestimable wealth that remain undiscovered to this day. An island home to strange and fantastic animals, experienced by a fortunate few lucky enough to have returned to tell the tale.

Every few decades, the story of this island is revisited with a new author’s variation on the theme; writers such as Robert Louis Stevenson (Treasure Island), Edgar Wallace and Ruth Rose (King Kong) and Michael Crichton (Jurassic Park) have all mined this treasure-island vein and made their fortunes. But this archetypal treasure island is not to be found only on the maps of the imagination: it truly exists and is known today as Isla del Cocos, (or Cocos Island, to English speakers), although no one can be certain why it was thus named.

Cocos first appeared upon Frenchman Nicholas Desliens’ map of 1541 as Ile de Cocques – which means ‘nutshell island’ – a true mystery, for there are neither nutshells to be found upon the island nor does the island itself physically resembleanything like nutshells. The current usage of ‘Cocos’ is thought to be an anglicized derivation of the enigmatic French name. (The island was claimed as sovereign territory by the government of Costa Rica in 1869, making the ‘island’ into ‘isla’, but that still leaves the ‘cocos’ to the imagination.)

Cocos has an irregular coastline, which makes estimation of land area more a matter of opinion than a surveyor’s science, but it is roughly 5 miles long by 2 miles (12km x 5km) wide. The island was formed during a volcanic upheaval around two-and-a-half-million years ago and is composed from lava flows of basaltic rock, labacorite and andecite. Its landmass is made up of four mountain peaks, the highest of which is Cerro Yglesias, at 2,080ft (634m). Cocos receives an average of 25ft of rainfall per year, resulting in lush green foliage and plentiful waterfalls (up to 70 waterfalls of varying sizes, during the peak of the rainy season).

The island supports a verdant, high-altitude cloudforest – made possible by the abundant rainfall and surplus water stored in the porous reservoirs of the island itself – which is unique to Cocos alone of all the islands of the Eastern Tropical Pacific (Clipperton, the Revillagigedos, the Galápagos Islands, and Malpelo). Because of the heavy rainfall, the island is prone to frequent landslides, which somewhat accounts for its irregular geography. The island has two large bays with safe anchorages and sandy beaches on its north side: Chatham and Wafer. Just off Cocos are a series of smaller, basaltic, satellite rocks and islets, the largest of which is Isla Manuelita (formerly Nuez).

The terrestrial life of Cocos exhibits a high number of endemic plant species (around 70) out of the 235 vascular plant species identified; 25 species of moss; 27 species of liverwort and 85 species of fungus. There are upwards of 87 bird species, including the endemic Cocos Island cuckoo, finch and flycatcher. There are 362 species of insect, of which 64 are endemic, andtwo endemic reptiles. Beneath the waterfalls and in the rivers are freshwater fish that mystify scientists with their very existence.

The history of Cocos Island is rich with pirates and explorers, adventurers and dreamers. Portuguese Captain João Cabezas is thought to have been the first to have made a written record of the island in 1526, but whether it was ‘known’ prior to that orif Cabezas could claim to be ‘the first to discover it’ remains unknown.

Because of its remote location and abundance of fresh water, Cocos has long been a favourite waystation for pirates, whalers and sailors. Early visitors introduced pigs and deer to the island as a self-perpetuating source of fresh meat; to this day, feral pigs and deer abound, much to the detriment of the island’s indigenous ground-nesting birds; and responsible for hastening soil erosion by vegetation degradation.

In 1685, buccaneers led by Captain Edward Davis sacked the city of León in Nicaragua. They chose Cocos as the site to hide their treasure, thus beginning a tradition and the island’s reputation – and ultimately an enduring legend, of ill-gotten, untold wealth hidden on Cocos Island. This treasure was said to be buried in Chatham Bay, but whether it was later unearthed and removed is a matter of speculation.

The most valuable treasure said to be buried (or to have once been buried) on Cocos is the fabled Treasure of Lima. According to legend, in 1821 a Captain Thompson was entrusted with ten years’ accumulated wealth mined from the South American continent. He was supposed to safeguard thisproperty of the King of Spain by sailing well offshore for a period of time until invading armies advancing upon Lima, the capital of Peru, could be defeated and he could return the treasure to its rightful owner. It was supposed to be a charter with an honest sailing ship, with the king’s trusted guards in attendance ‘just in case’ but the temptation was said to be too great; Thompson and his men dispatched the guards and took off with the treasure that had been loaded on board. Naturally, Thompson chose Cocos as the spot to hide the treasure, said to be worth US$300 million (in today’s currency). Thompson was captured at a later date but the treasure has never been recovered.

This story of The Treasure of Lima and Cocos’s role as island depository served as the inspiration for Robert Louis Stevenson’s book Treasure Island: a case of Cocos lore providing the basis for a fictional story and the fictional story, in turn, adding to the legend of the ‘true’ story.

Piracy was a lucrative industry in the 1800s and none was more successful than Benito ‘Bloody Sword’ Bonito, a Portuguese sailor turned pirate. After a prosperous run in the Atlantic, and with the British Admiralty actively hunting him, Bonito moved on to the west coast of the New World, plying his trade from the coasts of Mexico to Chile. The Spanish outposts were simply too far from Europe and thus poorly defended. Tremendous quantities of gold were being mined and taken from Mexico by the Spaniards, and Bonito and his men successfully took it from them. They had a glut of gold and jewels and a problem that was perpetual to pirates – that of where to store their loot so that it would be safe from… pirates. In 1865 however, the answer was Cocos, which Bonito found perfect as a base for operations. However, his men disagreed about keeping both their share and themselves in a place remote from the ‘enjoyments’ their loot could buy.

After putting down a near-mutiny by some of them, Bonito reluctantly agreed to divide up their cache of treasure, with the traditional ‘Captain’s Third’ to himself and the rest divided among his men. With one of the prerequisites of being a pirate being dishonesty, each individual is rumoured then to have gone off, in secret, and buried their treasures in a spot known only to themselves; so that they might return to the island, at another time, and recover their own personal shares without fear of treachery from shipmates.

Bonito would have needed a good deal of help with his shares of the treasure and it is said that he blindfolded men and had them carry his haul over the island before digging holes and then burying it. He then brought the men back to the ship, still blindfolded, so that he was the only one to know where exactly the treasure was buried. The stuff of legend, if not logic. Bonito died in battle some time later and his men were caught and hanged. And the treasure? No one can say forcertain. Many have searched Cocos but no one has claimed – nor can offer proof – to have found it.

Over the years many treasure-hunters have mounted expeditions to Cocos. A man named August Gissler was granted half-ownership of the island while he spent 19 years and tens of thousands of dollars searching for the treasures of Cocos. Unsuccessfully. Many partnerships were formed, and treasure companies descended upon Cocos using the most modern of technologies available and expending countless man-hours in search of the stuff of legends. Unsuccessfully.
Quite possibly, more money has been spent searching for treasure on Cocos than could realistically be buried there. It is said that more than 500 expeditions of varying size and degree of seriousness have been conducted on Cocos, looking for any treasure whatsoever. Most recently, the Costa Rican government has sold permits for hundreds of thousands of dollars to allow new generations of treasure-hunters, with the latest, greatest, sure-fire technology, to continue the search. Regardless of the failures of past treasure seekers, you can be certain that out there, right now, are new expeditions being planned; for as long as there is the lure of buried treasure, there are schemers and dreamers who think they know better – or will have more luck – than those who have gone before.
One thing is without doubt: the only tangible treasures to be found at Cocos with any certainty are its scenic beauty and its richly abundant sealife.

The first major scientific survey expedition of Cocos in the 20th century took place in 1925 when the New York Zoological Society mounted its first oceanographic expedition, to the Pacific, on a millionaire’s borrowed yacht, the 2,400-tonne Arcturus. On board was the organization’s director of Tropical Research, William Beebe; a man who would reach the heights (well, actually depths) of fame and exploration in 1934, when he and Otis Barton climbed into a small, steel bathysphere and descended half a mile down into the ocean off Bermuda. He was one of the first to visit Cocos and write about it and its sealife for mass readership; his written accounts of exploration and adventure in South America, at Galápagos and Cocos were bestsellers of their day.

Beebe was also the first man to dive by himself, beneath the waters of Cocos, to a depth of 30ft, in a 60lb copper diving helmet with surface-supplied air. He describes battling strong currents at the site of his singular dive (recognizable today as the shallow reef of Manuelita in Chatham Bay) with its abundance of surgeonfish, triggerfish and plentiful whitetip reef sharks. He sighted a tiger shark he estimated to be 18ft long and described his moments of apprehension: ‘There could be no thought of escape by flight. I crouched close to my wisp of sea-fan, although hiding behind it was as effective as an attempt to conceal oneself behind a handful of ostrich feathers.’ But the shark, uninterested, swam off and disappeared, leaving Beebe to surface, and write his popular book The Arcturus Adventure.

Two other members of the expedition were historian Ruth Rose and assistant of photography Ernest B. Schoedsack. Both would be so inspired by their visit that when their careers took them to Hollywood a few years later, Cocos Island would provide the inspiration for the remote and mysterious island home of King Kong in the classic film of the same name. (Ruth Rose went on to co-write the film’s novelization with Edgar Wallace; Schoedsack co-produced the film.)

American President Franklin Delano Roosevelt was fascinated by Cocos Island, visiting it and its high-profile treasure-hunting expeditions in 1935, 1938 and 1940. During his first visit, the President went fishing in the rich waters and was rewarded with catching and landing a sailfish; a first for an acting US president. In honour of his visits, an endemic species of palm tree was named after him: Rooseveltia frankliniana.

Austrian diving pioneers Hans and Lotte Hass sailed to Cocos on the Xarifa for an underwater filming expedition in 1954. Using their oxygen rebreathers, the team dived the northern coast of Cocos, at Wafer and Chatham Bays. Hass’s experiences led him to write (in We Come From the Sea): ‘Cocos may be the prototype of all treasure islands but it is surely also to be reckoned as the foremost of all shark islands.’ On his dives, Hass noted the abundance of whitetip reef sharks, sharks which – as he describes them – can only be silvertip sharks, large hammerhead sharks and he even had an encounter with two tiger sharks, all of which he captured on film at the time.

It is interesting to note that both Beebe and Hass had tiger shark encounters on their visits to Cocos, but there have been no substantiated sightings of tiger sharks among the tens of thousands of dives that have occurred since Cocos became a major scuba diving destination in the late 1980s. The question is: what happened to the tiger sharks? Have they become so shy – or have they been wiped out?

In the mid-Seventies, Jacques Cousteau’s son, Philippe, flew the Cousteau team’s seaplane to Cocos to make a general reconnaissance. Philippe and his crew landed in Chatham Bay and deployed an inflatable to visit the shores. They studied the rock inscriptions made by passing sailors and examined the abandoned excavations of departed treasure-hunters. The team had the opportunity to make a few scuba dives and its members were enthralled with the abundance and diversity of sealife. They did not have the chance to fully explore the island and the seas around it, but the potential was so full of promise that they intended to return and explore more fully at a later date.
Tragically, Philippe was killed in a plane crash before he could return with a full diving expedition, but the Calypso’s sister ship, Alcyone, came to Cocos in the 1980s to carry on the exploration and Philippe’s legacy.

While filming at Cocos, the Cousteau team made an obligatory, cursory search for treasure and ended up finding the wreckage of an American B-24 bomber that had inexplicably crashed into the side of Cerro Yglesias in 1943. One of the many discoveries made during the dives at Cocos was the presence of a soccer field-sized sea mount rising from deep water a mile offshore of the south side of the island. This sea mount is now known as Alcyone (after the ship) and it serves as a gathering point for vast schools of pelagic fish and a resident population of scalloped hammerhead sharks.

A more disturbing discovery was the prevalence and impact of unchecked illegal fishing. Although Cocos Island had been designated as a National Park by the Costa Rican government in 1978 (and granted further ‘protected status’ in 1982) with commercial fishing banned within 3km of the island, fishermen wholly ignored and violated the law. Transient boats from the Costa Rican mainland and Ecuador routinely sailed to Cocos to poach lobster and longline sharks and other pelagic fish. A handful of men had been stationed on the island to protect the new park, but without even a patrol boat they were completely ineffective at stopping the illegal fishing. According to the Cousteaus, some fishermen were taking 800lbs of lobster per trip and untold numbers of sharks, most of which were finned (the deplorable practice of cutting the fins off living sharks and dumping their finless bodies back into the sea).

The Costa Rican government was forced to start addressing the illegal fishing problem when Cocos Island became an international scuba diving destination in the 1980s. The first ‘dive boats’ were mostly sailboats, such as the Victoria and the Evoi, and they made intermittent visits a few times a year, bringing fewer than a dozen divers at a time. These early boats were geared for only the most intrepid and adventurous travellers and were simple, unsophisticated operations. The use of these vessels ended in the late 1980s and in the 1990s were superseded by the arrival of larger, regularly scheduled, dedicated liveaboard ships: the Okeanos Aggressor; Undersea Hunter; and Seahunter.
The arrival of these heavily advertised, professional diving operations changed the face of Cocos diving by bringing comfort and safety to one of the most remote diving destinations. These operations and their owners also changed Cocos Island itself by bringing hundreds of visitors each year, including journalists and proactive environmentalists, both of whom paid a national park fee (which, ideally, was to help fund the rangers) and more importantly, brought worldwide publicity to this remote island and its environmental problems. Thousands of articles appeared in numerous magazines as diverse as Forbes, Stern and Paris Match, in addition to most wildlife, outdoor adventure and scuba diving magazine around the world. Strangely, the only magazine not to do a feature on Cocos was National Geographic.

The new accessibility to Cocos for visitors also brought access for film and television productions, as well as worldwide attention to a place that was once upon a time, little more than just a rumour. In the past 15 years, there have been literally dozens of television documentaries and hundreds of new features filmed at Cocos, the most famous (and best) of which was Howard and Michele Hall’s recent IMAX production, Island of the Sharks (1999). The positive effect of all this publicity was to cajole the Costa Rican government into taking some positive action to protect its own resources.

With dive boats making regular itineraries to Cocos Island, the Park Service had, for the first time, a regular link with the island. Being stationed on Cocos was no longer a case of being stranded for an open-ended period of time. There was now a regular supply line: bringing fresh food to the park service and materials to expand its facilities, as well as transferring visiting researchers and rotating shifts of park service rangers. The competing dive operators joined forces to donate radios and a small patrol boat and an engine so the rangers could intercept (or at least witness) illegal fishing at sea. Slowly, the park service stationed on Cocos, under the direction of the late Joaquim Alvarado, began to expand its base of operations and to extend its influence to interdicting illegal fishing and to making policy with government support.

Still, it was and remains an uphill battle. While poaching of the lobster has been eliminated, illegal longline fishing continues at the periphery and often – emboldened at night by the cover of darkness – within the park’s nautical boundaries. The longline sets, which are often mile upon mile in length, do drift with the currents and regularly sweep through the park’s waters, taking sharks, tuna and billfish without regard to park boundaries. It is not unusual to find longline sets wrapped around Cocos’ pinnacles, taken by the currents and leaving evidence of the carnage of their catch upon the sea bottom.

The Costa Rican Navy occasionally sends patrol boats to intercept illegal fishing boats but unfortunately, they catch only a small percentage of the violators. Fines, confiscation of equipment and imprisonment of fishermen is rarely enforced in a country where familial ties and payoffs are a way of life.

Cocos Island may perhaps be the crown jewel of the Costa Rica National Park system; sadly, very few Costa Ricans, save a few park service rangers, employees of the dive operations and illegal fishermen, have ever or will ever visit ithe island. Thus the question is: How can a country be expected to protect a resource which most of its own people will never see (except in seafood markets)? A park, which is, although proudly spoken of by Costa Ricans (again, who have never been there), derided or shrugged off as being ‘for the ‘gringos’. (Currently, Cocos receives around 1,200 visitors a year; almost all are scuba divers, from countries other than Costa Rica, the majority of whom never set foot upon the shore of Cocos Island.)

In spite of the seemingly insolvable illegal fishing problem, non-governmental organizations have poured vast sums of money into Cocos to try at least to foster an atmosphere of conservation. Slowly, the Costa Rican government has responded with somewhat tighter enforcement measures and by doing so, after more than a decade of lobbying by these organizations, Cocos Island was designated a United Nations World Heritage site in 1997. If the people of Costa Rica can preserve Cocos Island and its waters, then the true treasure of the Cocos Island can be kept safe and enjoyed by many generations to come.

The diver’s first view of Cocos Island will typically be in the pale light of dawn; it’s a refreshing sight after the monotony of a 35-hour voyage from the mainland. One by one, divers blearily emerge from their cabins, roused by the clatter of the anchor. Only a few cursory pleasantries are exchanged as they pad about the deck, marvelling at the view. From the impenetrable jungle, swarms of sea birds wheel and circle, screeching their welcome. In the frenzy of imagination that accompanies the first sighting of Cocos, you could be forgiven for thinking they are pterodactyls, soaring on prehistoric thermals. Before long, the emergent sun is blazing down with equatorial intensity, bathing the island’s lush slopes in light. The scene is utterly spellbinding, but the divers are even more interested in what awaits them under the water.

Let’s pick a typical site at Cocos and go for a dive. The unpredictable nature of the island and its visitors means that each site is in a constant state of flux, but the sea mount known as Alcyone was consistently providing rewarding encounters at the time of writing. In many ways, Alcyone offers a good, broad introduction to Cocos, as many of the island’s marine visitors congregate there in large numbers.

The chase boats (pangas), take you on a picturesque tour along the eastern side of Cocos, then down the southern shore, where sheer cliffs plunge into the ocean. Above the cliffs, the summit of Mount Yglesias is shrouded in a perpetual mist, as if the island itself is reluctant to give up its secrets. The brief boat-ride takes you to a place off the southwest point, where the dive guides deploy a small anchor.

This is essential for a safe descent, as the currents that blast this submerged pinnacle are unpredictable. At the surface it may seem motionless, but a current could blow you clean off the site by the time you have reached 15m. So, you descend with a wary hand on the anchor-line, gazing down into the blue-grey infinity. For a while, you think the whole dive may be some cruel hoax, that the anchor is just hanging in blue water and the dive guides are having a joke at your expense back on the boat. They’re not. After a few moments (the descent is on a diagonal rather than a vertical line, so it can take three or four minutes), an outline of the sea mount appears below you. A few unthinking divers may choose to let go of the line before reaching the mount, but they could be letting themselves in for an exhausting swim. Keep a hand on the line until the descent is complete.

On the way down, you will see small groups of hammerhead sharks swimming over the sea mount. From above they are dark grey, and very hard to spot: you have to look for their trademark swaying movements. As more divers arrive at the site, the sharks will mostly be seen over the drop-off, although some will occasionally swim right over your head.

The shallowest part of Alcyone is about 26m below the surface. The top of the sea mount is about the size of three tennis courts, with drop-offs on all sides. Although you can find sporadic patches of coral all around Cocos, Alcyone’s topography consists of jagged volcanic rock and patches of white sand. Long spined black sea urchins are ubiquitous. Reef whitetip sharks (Triaenodon obesus) are everywhere: most of them are content to laze on the rock in groups of up to 15, their jaws opening and closing slightly as they move water over their gills.
Marbled rays (Taeniura meyeni) are similarly content to spend their idle hours resting in large groups. When you approach to within less than a metre, the rays move off with a gentle roll, often displaying the stinging barb at the end of their tails. They are not aggressive, and appear only mildly irritated by the intrusions occasionally made by curious divers.

There are always large aggregations of fish on sea mounts such as Alcyone. Immediately noticeable are the predatory jacks which constantly swoop over its lunar surface, testing the ubiquitous Pacific creolefish (Paranthias colonus), a cousin of the grouper that provides the basis of the diet for larger predators here. Over the course of a week’s diving, you will probably see a dozen different jack species, but here at Alcyone, thuggish bluefin trevally (Caranx melamphygus) and almaco jacks (Seriola rivoliana) dominate.

The almacos grow to more than a metre in length, and have absolutely no fear of divers. Sometimes they brush their silver flanks against divers to dislodge parasites: it can be alarming if you don’t understand what they’re doing! If you want to have a good dive at Alcyone, or at any submerged sea mount dive at Cocos, head into the current. It won’t do to fin like a madman for the duration of the dive, but you should swim to the drop-off where you should try to wedge yourself into a comfortable position from where you can watch out for one of the most spectacular sights in the natural world.

If Cocos Island is famous for one thing, it is the scalloped hammerhead sharks (Sphyrna lewini) that congregate in schools of hundreds, often thousands. It’s possible to see such schools at other sites in tropical waters, but Cocos and Malpelo (and possibly Wolf and Darwin islands in the Galápagos) are the only places where schooling hammerheads in large numbers are virtually a guaranteed sight.

Studies on scalloped hammerheads in the 1980s showed that their swimming patterns are highly directional; they swim around the sea mount in expansive circles, with only slight changes in course over long periods. Marine biologist Peter Klimley describes sea mounts as hubs around which large schools of hammerheads like to cluster. The sharks map out their journey by the invisible magnetic valleys and ridges which radiate like wheel spokes from these geological formations. It has been shown that hammerheads are both long-distance and vertical migrators, following the magnetic roads to deep-water feeding grounds by night, gorging on a meal of squid, then returning to the shallower waters at the top of the sea mount at dawn. This nightly round trip is a remarkable feat of navigation, because the sharks are not able to use the surface or the sea bed for specific routes with the help of their highly developed sensory apparatus.

There has been much debate over the likely reason for the shark’s distinctive features. It is widely accepted that the ‘hammer’ design succeeds in spreading the shark’s electromagnetic receptors, eyes and nostrils over a larger area. In fact, the feature could have a dual purpose: studies have suggested that the broad, flat head gives the shark added lift when swimming, like the design of a hydroplane. It also seems to increase the manoeuvrability of the shark, possibly by decreasing the turning radius. One writer, Paul Budfer, has suggested that the lobes may also be a detriment, and could be easily be damaged in a tussle with a tiger shark or a great white shark. Budfer believes that hammerheads are the most recently-evolved of the sharks, and could represent something of a dead end in terms of evolution. ‘It’s really rather difficult to assign the concept of ‘detrimental development’ to an animal‘, ‘but overspecialization is thought to be one of the major causes of extinction.’

Watching the hammerheads swarm over Alcyone, it’s hard to regard them as one of Mother Nature’s botched experiments. Yet the sharks’ extreme sensitivity certainly makes them hard to approach. They abhor the sound – or possibly the disturbance – made by divers’ bubbles, so anyone who insists upon diving in a large group will not get close to the sharks. The best plan is to find a cleaning station manned either by barberfish (Johnrandallia nigrirostris) or king angelfish (Holacanthus passer). These cleaning stations are regularly visited by sharks, which are more likely to tolerate your close presence when they are being attended to by the cleaner fish.

More often than not, the buddy system is completely ignored at Alcyone; divers concentrate upon moderating their breathing as they peer into the blue, waiting for ghostly shadows to appear. It is easy to become absorbed by the vigil, but at Cocos anything is possible. At any point, the sea mount could be visited by oceanic wanderers, such as the silky and Galápagos sharks that are known to stop by. Or, as occurred earlier this year, a group of divers ignored the hammerheads entirely when an inquisitive whale shark arrived at Alcyone. It circled the sea mount repeatedly and then approached the divers at close quarters.

Faced with distractions such as these, it’s all too easy to
lose track of mundane considerations such as air and time. Even with the benefits of nitrox, you can only expect to get about 30 minutes on the sea mount before running into decompression. More potential decompression accidents take place at Alycone than any other site at Cocos, thanks to the beguiling combination of big fish, big walls and big currents. However, even as you make your way back up the anchor line, the show is not necessarily over.

The hammerheads can often be seen as shallow as 8m, and there is usually a curious wahoo (Acanthocybium solandri) waiting to entertain you during the final safety stop at 6m. It’s also worth keeping an eye out for mobula rays (Mobula tarapacana), diminutive cousins of the manta, which enjoy bathing in diver’s bubbles. Never try to follow or chase a mobula ray: they will approach you quite closely if you stay still and breathe out lots of bubbles. Schools of up to a dozen rays – known as Chilean devil rays in Central America – are regularly seen at Cocos. Alcyone’s strength is that it encapsulates the key elements of Cocos in a single dive, but if you really want to appreciate the complexity of the island’s marine ecosystem, you have to visit some of the other famous sites.

Check-out dives are usually carried out at Manuelita Island, the largest of Cocos’ satellite islands. The front side of Manuelita faces the open sea and offers a good chance of seeing hammerhead schools. This is also a good site for manta rays (Manta birostris), which can occasionally be seen soaring along the wall, scooping planktonic snacks into their capacious maws. The dive presents you with a sloping wall, strewn with house-sized boulders. Every surface is plastered with macro oddities: algae, hydroids, Christmas tree worms and countless tiny blennies, which dart in and out of their holes. The most common of these is the endemic Cocos barnacle blenny (Acanthemblemaria atrata), which is seen practically everywhere at Cocos up to a depth of 20m. There must be millions of these fish around the island.

Night dives are usually carried out on Manuelita’s rear side, which faces the sheltered waters of Chatham Bay. It is bordered by a shallow coral reef that offers countless opportunities for macro photographers. It is a common misunderstanding that Cocos is devoid of coral growth, but there are several reefs here, living at the edge of their physiological tolerance limits for temperature (both hot and cold, due to the many currents that converge on Cocos) and water clarity. Before the El Niño event of 1983, the coral gardens at Cocos were considered some of the best in the eastern Pacific.

There is not a great variety of coral here, as the larvae have to survive an 8,000km journey from the Line Islands of the central Pacific. It is thought 90 per cent of the coral died during the 1983 El Niño, and the damage from the even stronger 1997/98 event has yet to be assessed. Since 1992, only six of the 19 shallow-water coral species previously seen at Cocos have been observed on the reefs. Meanwhile, the increased availability of algae (which rapidly colonize the coral skeleton) has fuelled the march of sea urchins, which advance across the reefs in great huddles, like huge black porcupines. Still, night dives offer a chance to track down the shy jewel moray (Muraena lentiginosa), which continually opens and closes its mouth to breathe.

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