El Niño triggered bleaching at Cocos, in
which a coral polyp expels its symbiotic algae, turning it white.
Hammerheads or Bust
by Ken Mallory
September 23, 1998
Cocos Island is renowned for its hammerhead sharks. Typically, hundreds of
scalloped hammerheads will congregate in the deep, current-whipped waters
swirling around this ancient volcano. Yet during the first half of 1998, the
warmer waters brought by El Niño had apparently kept the hammerheads and
other large, ocean-going predators away (and caused serious bleaching of corals
on the island's reefs). Hammerheads are camera-shy under the best of
circumstances, but when surface water temperatures reach 82°F and
higher, divers rarely see them.
So it was with some anxiousness that I arrived at Cocos Island last July. I had
come to visit Howard and Michele Hall as they continued shooting their IMAX
film "Island of the Sharks." The film is being funded in part by my employer,
the New England Aquarium, and we knew that hammers might make or break the
film. Had they returned?
Cocos Island was recently ranked as the number-one spot in
the Pacific Ocean for advanced scuba diving.
Not long after I arrived I dove at a site known as Dirty Rock. My instructions
were to follow the current along the coral-encrusted wall until I came to the
far end. To see hammerheads, I was told, I would have to leave the relative
security of the islet's flank and launch off into the blue. If I went in the
right direction, I would find a submerged mountain after several hundred feet,
and it was there I might find hammerheads swimming up from the depths. If they
Despite my aquarium credentials, I'm more comfortable on land than in the
water, and the idea of going off into the blue was a little like doing a
freefall blindfolded, with no assurance of where I might end up. I was deep
enough not to be aware of the surface, and the sea was a rich blue all around
me, with an even darker, murkier blue below. Peering through my face mask for
some sign of life, all I could see was the slow paddling of the occasional
Scalloped hammerheads are typically
wary of scuba bubbles.
Then I heard a dull but distinct sound. Someone was pounding on his scuba tank—the universal symbol among divers to pay attention. Following a pointed
finger, I looked below and there, not 25 feet under my belly, was a parade of
seven hammerheads. They were swimming in single file, swinging their peculiar
boomerang heads back and forth and probing the water with their
high-sensitivity snouts. One after the other scurried obliviously past me until
each faded into the endless blue.
The hammerheads were back. To our dive masters, who study the currents around
Cocos as a way of predicting where to see wildlife, the currents on that and
subsequent days said "hammerhead." And the currents didn't lie. Over the coming
days, the Halls used their 250-pound IMAX camera to film hammerheads and many
other pelagic fish through the oily veil of thermoclines that send fingers of
cold current through the surrounding warm water. At a dive site called Alcyone,
they were even treated to a hammerhead gathering in the hundreds.
But seeing such large schools on the edge of one's vision and getting them
close enough for the money shot in an IMAX format—as close as 10 to 15 feet
in front of the lens—are two different matters. That was the challenge of
the Halls' last few days in early August, and will be the focus of their final
trip to Cocos over the coming days and weeks. Join them by bookmarking this
site and following the expedition as it unfolds.
Kenneth Mallory is Editor-in-Chief of Publishing Programs at the New England
Aquarium, which is co-producing "Island of the Sharks" with WGBH-TV. He is
currently writing a children's book to accompany the film. Further dispatches
in this series will be submitted by NOVA Online producer Peter Tyson, who
arrives at Cocos Island with the Halls on September 25th.