It is a sunny afternoon at Wolf Island in the northern Galapagos; the surface of the water is mirror calm and the only sounds are the calls of the frigate birds in the high cliffs overlooking us. The divers, still a bit sleepy after the traditional post-lunch nap, are helped down from the Galapagos Sky liveaboard to the waiting Zodiacs, which ferry them along the wall to an area known as ‘Landslide’, where the volcanic cliff has broken and tumbled into the Pacific.
On the count of three we lean backwards and fall into the ocean, the brightness of the afternoon replaced with the muted hues of the underwater world. Following the pre-dive brief, we do not pause to collect ourselves, but descend without hesitating to 12 metres, at which depth we recheck our equipment, turn on cameras and ensure we are ready for everything Wolf has to throw at us.
Underwater, Wolf Island has many attractions. The mid-water zone is dominated by one species in particular, the creole fish, which occur in such great numbers there are times when they seem to block out the sun. Also high up in the water column are sleek predators such as tuna and trevally; they dart around the fallen boulders along the reef slope, looking to spook a reef fish into breaking cover.
We continue the descent, finally coming to rest at 25 metres, where dive guide Max Castillo – resplendent in a bright orange ‘Finding Nemo’ hood – signals that we should form a line and crouch low on the reef. I feel a surge of cool water and a chill runs – literally – along my spine as the water ingress registers along my wetsuit zip. We are in the zone of the thermocline, where layers of warm surface water meet cool, nutrient-rich upwellings from below. It is a border land between the creatures of the darkness, and those associated with the daylight shift of the reef. This is the place where scalloped hammerheads come to be cleaned. During the night, the hammerheads are busy hunting squid at abyssal depths. No-one knows quite how it is played out, but somehow they pick up parasitic copepods, which attach themselves to mating scars around the sharks’ gills.
Hammerheads are sensitive animals, and they make frequent visits to cleaning stations ‘staffed’ by king angelfish and barberfish, which billow out from the safety of the reef to peck the copepods from the sharks’ silvery flanks. It is a fascinating ritual, one of the classic examples of symbiotic mutualism – the shark is relieved of its irritating parasites, and the cleaner fish enjoy a nourishing meal. However, when it comes to scalloped hammerheads nothing is easy. To get a good clear photograph you have to be within two metres, and getting that close is difficult with a super fast, super-sensitised animal that happens to loathe bubbles. I watch the blue as the sharks steam by in vast schools on the limits of visibility. The water around the thermocline is hazy, it’s hard to make out the shifting shapes.
At times it seems as if the hammerheads are conducting some strange dance, as the water swirls around them like Picasso’s Starry Night. Finally, I see a group of sharks breaking from the school. They head towards the reef, swinging their great heads from side to side, searching for an active cleaning station away from the column of bubbles. I position myself behind a rock a few metres from a cleaning station. Sure enough, one of the sharks peels away and heads right towards my rock, slowing down to a gentle cruise as it nears the barberfish. They stream up into the water and set to work as the shark does its best to slow down (the only time hammerheads actually come to a halt is during mating).
The spectacle has all the urgency of a Formula One car on a pit stop; in a matter of seconds, the barberfish complete their business and head back down to the reef, while the shark gives a final shrug of its head and heads off to re-join the dance of the hammerheads, out there in the infinite blue of the eastern Pacific.