At dawn on Friday 8 November 2013, exactly three years ago, the Philippines was struck by the deadliest typhoon in its history: Typhoon Haiyan.

The first point of impact was the eastern province of Guiuan. From there the 370-mile-wide storm travelled west across the country, devastating its picture-perfect islands before moving on to Vietnam and Laos.

As the 195mph winds struck the shore, palm trees crunched into two, buildings were ripped apart, and cars were swept up and piled on top of one another. Over the course of the next 48 hours, more than a million homes were destroyed and more than 6,000 people were killed.

In the days that followed, journalists reported scenes of utter devastation: splinters of wood and glass were smashed all over the ground, and debris littered the once-pristine beaches. Images went viral of children walking over rubble, and of hand-painted signs stacked up saying, "Help us!" and "We need water, food, shelter". Everywhere, lives and livelihoods had been reduced to dust.

Malapascua, a small island resort that lay right in Haiyan's path, was particularly hard-hit. Buildings were flattened, fishing boats annihilated, and all power and communications lost. To most, it seemed that this once-popular tourist destination was finished. But all hope was not lost: Malapascua still had its thresher sharks.

Thresher sharks are long-tailed creatures that use their tails as whips to stun other fish, making them easier to catch.

Early in the morning some of them come close to shore to avail the services of the cleaner wrasses

There are at least three species, all in the genus Alopias: pelagic thresher sharks, which are found in Malapascua; bigeyes, found in tropical oceans across the globe; and common thresher sharks, which prefer cooler waters. The Philippines' pelagic threshers can be distinguished by the dark shading over the base of the pectoral fins. They are also the smallest of the three species, only reaching around 10ft (3m) long when fully grown.

All three species of thresher shark are highly migratory, and are found both in high seas and shore waters. They only reproduce slowly, according to the IUCN Red List of Threatened Species. Pelagic threshers produce just two offspring a year and do not reach sexual maturity until they are around 8 years old.

Every day, pelagic thresher sharks head to Monad Shoal, a sunken island just off the coast of Malapascua. They have chosen this spot for a good reason, says Alessandro Ponzo, executive director of the Large Marine Vertebrates Project Philippines.

"Thresher sharks, like all other wild species, host a number of external parasites," says Ponzo. "To get rid of them, early in the morning some of them come close to shore to avail the services of the cleaner wrasses [small fish] at several cleaning stations that can be found around Monad Shoal."

These "cleaning stations" lie along the rocky edge of the sea mount. "The sharks approach the area and hover to allow the fishes to remove the parasites from [their] bodies," he says.

Thresher shark tourism was in full swing within weeks

The shoal is also surrounded by deep water filled with sardines. That means the sharks, which spend the daytime in the dark water, can hunt and feed.

Divers have been coming to the region since 1999 to witness this natural marvel for themselves. Each morning the divers wait on the sea mount edge, 66ft (20m) below the surface, for the sharks to approach.

"There are no cages or baiting involved in our thresher shark tourism," says Anna Oposa, co-founder of campaign group Save Philippine Seas. "The sharks are there because they come to clean themselves on the reef every day."

Oposa says the thresher sharks have been fundamental in helping Malapascua to recover from Typhoon Haiyan.

"Thresher shark tourism helped rebuild the island for two reasons," says Oposa. "One, because… past and present tourists love Malapascua and its people so much, a lot of help came in – and two, the sharks were not affected by the storm, so thresher shark tourism was in full swing within weeks, which brought income to the island."

When I returned to Malapascua a few days after Haiyan, I didn't recognise it

Steve De Neef is a photojournalist who lived in the Philippines and travelled extensively across the country in the aftermath of Haiyan to document the devastation. "Two days after the typhoon, some of the locals went out on one of the only boats that was still working to check on Monad Shoal and assess the damage," he says. "Luckily the shoal didn't receive extensive damage and the sharks were still around."

After two weeks, shark tourism was back in business. At first, divers cancelled their trips, but when word got out that the diving was up and running again, the divers returned. "[They] actually went very early on to dive at Monad Shoal, without the regular crowd, so they would have the thresher sharks to themselves," says De Neef.

Thanks to its ecotourism industry, Malapascua has been almost entirely restored.

"When I returned to Malapascua a few days after Haiyan, I didn't recognise it," says Oposa. "It looked like a giant stepped on it. I remember getting lost many times because the landmarks were gone, like little huts or structures."

Three years on, the devastation is virtually gone.

For me thresher sharks are a gift to Malapascua

"It's almost back to normal," says Oposa. "Houses, resorts, and dive shops have been rebuilt. Some locals have said that their homes are now stronger… because of the aid that came in. We're still rebuilding one structure in the elementary school, but many houses have been rebuilt, and all dive shops have been rebuilt as well."

Locals are well aware of the central role thresher shark tourism has played in maintaining their livelihoods.

Dennis Bait-it is a dive instructor in Malapascua and a member of Project Sharklink, which provides training and information on the benefits of shark conservation tourism. "I get my income from the thresher sharks, as do most of the locals on the island," he says. "There are shark dive managers who started off as fishermen… people are happy because their children can go to school, finish and become dive instructors."

"It's incredible how much the lives of people [on the island] are related to the threshers," says Oposa. "When you walk there you see [the sharks] in paintings, murals, the signs over every dive shop."

Local souvenir shop owner Bryan Barcenas crafts sculptures of the sharks out of wood to sell to tourists. "[The sharks are important] in Malapascua because they provide a lot of work to people here," he says. "It's good business for me because [after the tourists have done their diving] they come and buy a wooden thresher shark. For me thresher sharks are a gift to Malapascua."

Thresher shark fins represent about 2.3% of the fins bought and sold annually in Hong Kong

Former fisherman Renato Reuyan has also rebuilt his life using his thresher shark business. Until recently he hunted the sharks to supply the huge shark fin market in Asia, but has since turned to protecting them.

"Before, sharks meant nothing to us," says Reuyan. "When we caught a shark we would be happy, and in one night of fishing I could catch five to 10 sharks."

He does not do that any more. "[Once I realised] it is important to protect the island, I became a dive guide," he says. "Now, if there are no more sharks and then I don't have any income, my family would go hungry. More sharks mean more divers, which means more income."

Sadly, despite the enthusiasm of the people in Malapascua, thresher shark tourism still faces serious challenges.

"Thresher sharks are seen in other areas of the Philippines, but illegal and commercial fishing is taking away [tourism] opportunities from these regions," says Oposa.

Thresher shark fins represent about 2.3% of the fins bought and sold annually in Hong Kong, the largest market for shark fins, according to a 2006 study published in Conservation Biology. This equates to millions of thresher sharks killed every year.

Before, sharks meant nothing to us

"[Illegal fishing] is a constant threat when there are commercial fishing boats fishing nearby," says Bait-it. "We have a group of men who patrol the shoal 24/7 to shoo [them] away."

"Sharks are facing a global mortality crisis, with 100 million killed every year," says Luke Warwick, director of Global Shark Conservation at the Pew Charitable Trusts. "Thresher sharks can take over 10 years to mature and bear pups, with threshers only having one or two pups every other year. Add to that the unsustainable declines these species are facing, at least 70% everywhere they are found… and these sharks are headed toward extinction."

Nevertheless, Bait-it and his team are doing all they can to encourage tourists to visit Malapascua and protect the sharks. He believes the positive impact of thresher shark tourism extends right across the country. "From Manila, it's a one-hour flight and then a land trip, then a boat [to get to the island]," he says. "If people come all the way here, they'll go elsewhere too. The rest of the Philippines also benefits."

The thresher sharks could yet continue to help the Philippines recover after Typhoon Haiyan, by thrilling scuba divers day after day. But only if they are alive for the tourists to marvel at.

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