This story appears in the October 2011 issue of National Geographic magazine.
The biggest fish in the sea is as long as a school bus, weighs as much as 50,000 pounds, and has a mouth that looks, head-on, wide enough to suck down a small car. Despite this distinctive profile, scientists know very little about Rhincodon typus—the whale shark.
The behemoths are indeed sharks: They breathe through gills, like fish. They are cold-blooded, like fish. The "whale" part of the name refers to size and how the animals eat. They are one of only three known shark species that filter feed, as baleen whales do, swimming slowly through plankton-rich water, maws agape. Water goes in carrying edibles of all sizes, and water sans food flows out.
The giant fish is hard to study in part because it is hard to find and track. By tagging individual specimens, scientists have learned that whale sharks can log thousands of miles in years-long trips. But they sometimes disappear for weeks, diving more than a mile down and resting in the chilly deep for a spell. No one has ever found mating or birthing grounds.
Whale sharks are ordinarily loners. But not in one corner of Indonesia. The photographs on these pages, shot some eight miles off the province of Papua, reveal a group of sharks that call on fishermen each day, zipping by one another, looking for handouts near the surface, and nosing the nets—a rare instance when the generally docile fish act, well, like the rest of the sharks.