I REMEMBER WATCHING, many years ago, a Cousteau episode about Clipperton Atoll. Impressive schools of scalloped hammerheads cruising over virgin reefs stuck in my memory.
Had things changed around the island? I wondered. Given the massive decrease in shark populations worldwide, what would the status of these apex predators be nowadays around such an isolated, uninhabited atoll?
As a shark advocate I was curious to find out, and the idea of organising an expedition to Clipperton was born.
Few people recognise the name when it is mentioned, and even fewer can begin to say where the atoll is. Located in a zone known as the ETP (Eastern Tropical Pacific), Clipperton lies about 900 miles south of Mexico’s west coast, on the same latitude as northern Costa Rica.
San Jose del Cabo on Baja California Sur is our departure point. With our expedition-type vessel and rough sea conditions expected, we will need 117 hours to reach this blip on the radar.
Its location may have earned it the title of most isolated atoll on the planet, but Clipperton’s history is surprising and complicated.
Magellan made the first discovery claim in 1521, but it was never proven that he saw the atoll. A later claim was made in 1711 by the French, who gave it the name l’Ile de la Passion because they said they discovered it on Good Friday.
The modern name derives from the English privateer John Clipperton, who is supposed to have used the island as a base camp, and perhaps buried treasure on it.
More recently several countries have disputed ownership of the lost atoll, including Mexico and the USA. In 1931, however, the matter was settled through international arbitration, and Clipperton was officially declared a French territory.
Today, anyone wishing to set foot on the island or enter the 12 nautical-mile zone around the atoll needs a permit from the French government. Such authorisations are rarely granted to foreigners and are almost entirely limited to scientific missions.
Like all atolls, Clipperton is a circular coral outcrop in the middle of which lies a lagoon. This is composed of fresh water – or rather, stagnant rain water – as no passes connect it to the sea.
Salt water enters the lagoon only if extreme surf conditions allow waves to cross its natural barrier during major storms or hurricanes. There are no fish, and decomposing organic matter has produced a layer of hydrogen sulphide trapped in its waters from 10m down. This phenomenon is encountered in many underwater caves round the world.
Exposure to hydrogen sulphide and the stagnant water can cause infections, burns and even temporary blindness, so diving in the lagoon is not advisable.
Clipperton has been uninhabited for more than 70 years, and because of its isolation from other landmasses, it has evolved in a similar manner to other remote islands such as the Galapagos.
It took a year of negotiations with the French authorities, but we finally received what we had dreamt about – permission to land on Clipperton and dive its waters! We team up with an esteemed group of shark scientists who will oversee and participate in our citizen-science diving expedition.
Following months of preparations and planning, the departure day finally arrives, and after five days of sailing we get our first glimpse of land.
Dark clouds linger over Clipperton, yet the sight of the atoll is comforting.

AS SO FEW DIVERS have explored the atoll’s reefs, no official dive-maps exist. We choose to dive various areas based on topography and surf conditions. Finding names for the dive-sites will become part of the nightly entertainment programme.
I’m impatient to see what’s hiding beneath the surface of the amazingly blue water surrounding the atoll. As I descend along a steep wall, my first impressions are delightful.
Water temperature is pleasantly warm at 30°C and the water very clear. The reefs are outstandingly healthy too, with an estimated 60-80% of living coral coverage – way above South Pacific standards.
Hard coral in various colours and shapes is abundant. Very little soft coral is seen, and the sand patches are rare.
Astonishing schools of fish of all sizes parade before us. We’re off to a very good start, and the underwater landscape is so beautiful that I find it difficult to decide where to point my camera.
As part of the citizen-science programme, we are gathering images for a census of reef species, so I need to put my emotions aside and concentrate on the task. I start with fish-identification photos, methodically targeting species
I encounter the most, and ending with the less obvious or numerous individuals.
One of the first aspects to surprise me are the high numbers of finespotted morays. We often spot several in the same area on our dives.
At Clipperton, there’s no need to look under rocks or in coral crevices. Here the morays are out to exercise. They swim along the reef and often follow divers around. They are high on the food chain and seem fearless.
The same can be said for the bluefin trevallies and black jack that appear to be everywhere, circling divers. Schooling in fair numbers, their sizes are impressive, and they patrol the reef as if they own it.
Time flies by, until my contents gauge reminds me that it’s time to head for the safety stop.
On the following dives, our group turns its attention to the atoll’s endemic species, intending to seek them out and perhaps even discover new ones. As at the Galapagos, the remoteness of Clipperton has contributed to the evolution of species found nowhere else in the world.
The first endemic fish to grab our attention is the Clipperton angelfish. It is easily recognized, not only by its blue colour but by the white spot near its tail.
Then there is the Clipperton gregory. This small damselfish measures 4-6cm and has very distinctive features. Its yellow head, brown body and white mark on its tail make it easy to spot. Like many species of damselfish, it is very territorial, especially when guarding its eggs.
Also endemic is the Clipperton grouper. While it is abundant on the reef, it can easily be mistaken for its cousin, the starry grouper. We have to watch out for the reddish V-shaped marking on its nose that stretches past both eyes.

THE SECOND PART of our underwater mission is to evaluate the health of the shark population in the waters around the atoll. Two methods are used: underwater observation and tagging with acoustic and satellite transmitters, which allows scientists to establish residency of sharks as well as migration patterns of the adults.
They hope to link Clipperton to well-known shark sanctuaries such as Cocos, Galapagos, Malpelo and Revillagigedos Archipelago (Socorro), and eventually establish a protected corridor for sharks between these islands.
Our first task is to retrieve and replace the receivers. On our way to retrieve one of these, our inflatable is escorted by a huge pod of hundreds of bottlenose dolphins, racing us and surfing the 2m waves with enviable ease.
We’re lucky, in that a few dolphins follow our descent to the receiver. Curious, they stay at a distance during the operation, making it difficult to concentrate on our work.
During our safety stop, we are greeted by a huge school of bigeye jack. As I swim towards the boat I notice another school, barely submerged, and as I get closer recognise them as steel pompanos.
It’s a surprising and pleasant end to a productive dive.
On every dive we carefully scan both the reef and the blue on the lookout for sharks, and on every dive we see many juvenile silvertips but only a few adults of the same species. The scientists conclude that the area is a silvertip nursery.
On a very few occasions we spot an adult Galapagos shark or scalloped hammerhead off in the distance, but not the walls of sharks we had been hoping to find. This is sadly not surprising, given the overwhelming evidence of long-lining we find everywhere on the reefs, and the numerous nets and buoys that have washed up onshore.
Our time in Clipperton has been brief. We have not been able to explore the north side of the atoll because of high winds, and a more optimistic scenario is that the sharks prefer the north side because it is exposed and currents are stronger there. It is also possible that because of lingering effects of the El Niño phenomenon, the sharks are simply in deeper waters.
As Clipperton slowly disappears into the distance, we feel that we have only scratched the surface of what this unique eco-system has to offer.
If the remoteness of the atoll has limited the number of species that visit or inhabit its waters, Clipperton’s coral coverage and biomass are impressive. We ran out of time to photograph and catalogue the smaller critters which, no doubt, harbour their own surprises.
Like many isolated islands, Clipperton is under heavy pressure. Intensive fishing of its waters is not without consequences. Protecting the atoll now appears vital to allow it to become the underwater oasis of life it used to be.