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Oslob, the Philippines (CNN) — It's 6 a.m. and nearly 100 tourists are gearing up excitedly on the beach at Oslob.
We're here to see the largest fish in the world, the whale shark -- measuring between 18 and 45 feet in length and up to 20 tons in weight -- in some of the clearest waters in the Philippines.
In groups of 10, travelers are helped onto tiny catamarans that look like they'll capsize if we make the wrong move.
We paddle out for a few minutes before cranking the engine, then cruise for another five until we reach the first cohort of feeders.
Our driver kills the engine, yelling cheerily: "Here we are! You want to get in?"
Of course I do.
I shove on my flippers (careful not to flip the boat), throw my life jacket off, and slip into the water.
Encountering the giants
Pumping my flippers until I'm clear of the group, I scan the water for dark, lumbering shadows.
A flurry of bubbles signals where to look, and a 20-foot whale shark looms into view.
Its tail alone is the length of my body and one swipe could do some serious damage.
Parasitic fish swarm the shark's body, feeding off debris on its belly and its giant spotted coat.
Their mouths gape wide, filtering vast amounts of water for food in the same way whales do.
Docile as dolphins but not nearly as energetic, it strikes me how unfazed the sharks are given the amount of unnatural activity there is in the water.
Oslob's whale shark tourism industry
Oslob's reputation as a whale shark spotting area began, it's said, when a tourist noticed their presence in the area and hired a fisherman to take him out to see the big fish.
Since then, its fame has spread.
"People first started coming to see the whale sharks in Oslob around three years ago, in 2012," explains Edgar Mirambel, founder of Island Trek Tours.
Popularity hasn't scared the whale sharks away.
A favorable environment and free feeding sessions -- krill, small fish and sea plants are on the menu -- from local fishermen keep them in the area.
Mirambel explains that Oslob was struggling to rely on farming and fishing until whale shark tourism began to draw the crowds to this sleepy, backwater town.
No petting. No sunscreen lotion.
Feeding sessions for the whale sharks start at 6 a.m., and last until noon.
Before each tour sets off, tourists are given a brief on the dos and don'ts.
Maintaining a distance of four feet is crucial -- there's a fine of $56 or even jail time for anyone who touches them.
Most tourist stay on the boats, but the handful of swimmers are told to wash off any sunscreen to keep the water pollutant-free.
Far too soon, our guide signals us back to the boats.
We chug back to shore before the next groups descend.
The experience is surreal and the whale sharks awesome.
But as with any activity that relies on nature or wildlife, it's not without its controversies.
Some have expressed concerns about the environmental impact of the tours.
Tourists began flocking to Oslob to see whale sharks in 2013.
An ethical fix
Dr. Alistair Dove, director of research and conservation at Georgia Aquarium, Atlanta, writes regularly about whale sharks.
He says they don't naturally congregate in Oslob in the way they do in other parts of the Philippines and are being lured.
"Itinerant sharks first began showing up around fishers [in Oslob] who were collecting krill at night. Over time, the fishers learned that they could feed the sharks with portions of their catch and began taking tourists out during the day and baiting whale sharks with krill."
Elizabeth Beneloga, tourism officer for the Municipality of Oslob, challenges Dove's account.
"The whale sharks in Oslob have been in our waters since time immemorial," she says. "The fishermen feed the whale sharks only to attract them to the water's surface -- it's a small amount of krill, and the feeding stops in the afternoon."
There's concern that feeding sessions leave the whale sharks' passive toward humans and more vulnerable as well as over-dependent on the handouts.
The interaction in Oslob has, however, raised awareness of the endangered fish (whale sharks became a protected species in 2003) across Asia and beyond.
It's also helping the local economy.
In 2014, whale sharks attracted over 110,000 tourists to Oslob, according to the Department of Tourism for Central Visayas, the islands of which Oslob is a part.
The majority are non-domestic, traveling from East Asia and North America.
"Our whale sharks contribute tremendously to Oslob's income, helping to create much needed infrastructure, jobs, and opportunities for growth with neighboring municipalities," says Beneloga.
She says nearly 300 staff work at the feeding site, under local government management, to safeguard the sea creatures.
Oslob is ripe with other natural beauties in addition to the whale sharks.
Among them are the waterfalls at Tumalog, which are worth the hair-raising moped ride down a precipitous hill.
The area resembles a scene from the blockbuster "Avatar," with a serene turquoise pool that attracts thirsty swallows and brave swimmers.
Paul and Madz Eatery (Tan-awan, 6025 Oslob) is a local restaurant on the next beach along from the whale sharks.
How to get there
Oslob can be reached by internal flight from Cebu to Dumaguete.
Ferries run from Sibulan port, Dumaguete to Liloan port, Oslob every hour from 5 a.m. The last ferry from Oslob is at 7:30 p.m. An adult fare is PHP 62 ($1.5).
It's best to go as early as possible to avoid the crowds, and the heat.
The charge for whale shark swimming is PHP1,000 ($23) for a half hour session. Fess can be paid in cash before the tour at Barangay Tan-awan Beach, Oslob.
Where to stay in Oslob