The warm, coastal waters off southern Cebu in the Philippines, are paradise for the whale shark. Growing to 12 metres in length, it's the world's largest fish. A filter feeder, it poses no great threat to humans. And for conservationists, that's a problem. An explosion of tourism in the region, led by organised whale shark feeding tours, is attracting the sharks in unprecedented numbers. Biologists like Alessandro Ponzo of the Italian conservation group Physalus, say the practice is unnatural and should be regulated. (SOUNDBITE) (English) DR ALESSANDRO PONZO, PRESIDENT OF PHYSALUS ,SAYING: "But here, the two behaviours, their natural behaviours, are combined into a new behaviour that we have never seen anywhere else. So they follow the boat, they learn to follow the boat, and that is the source of food. If you see a new shark coming, for the first week they are here, they don't know how to do it. They just swim around, bumping into other sharks tried to feed vertically. and it takes four to five days before to actually realize the food is coming from the hand of the person, and they make the association together." Ponzo fears that this conditioning could lead to the development of abnormally aggressive behaviour between the sharks and, over time, affect their ability to hunt naturally. Buit for the people of Oslob, the whale sharks are an important source of income. Ramonito Lagahid gave up fishing long ago. (SOUNDBITE) (English) RAMONITO LAGAHID, VICE-CHAIRMAN OF TAN-AWAN OSLOB SEA WARDEN AND FISHERMEN ASSOCIATION (TOSWFA), SAYING "Some people are asking to stop feeding, but if we stop feeding, what is our livelihood? For example we stop feeding, so, we back to our fishing business of what we are doing last time." And tourism is improving livelihoods along the entire coast. Income generated by shark feeding ticket sales is divided between the tour operators, the village and the wider municipality, and while impact studies are ongoing, Alessandro Ponzo acknowledges the power of profit. (SOUNDBITE) (English) DR ALESSANDRO PONZO, PRESIDENT OF PHYSALUS, SAYING: "If the impact is bad, or is manageable, it maybe be manageable if it's properly regulated here, in one place, if it's spread out in ten places, it would be impossible to control. On the other side no body wants to say no, because Cebu is the biggest electing, voting province in the Philippines and that something that brings millions of dollars into the local economy. It's a very good alternative for the people, so the local community enjoying it, there are pros and cons. So nobody have been wanting to take a position on it." And all the while, the tourists keep coming. (SOUNDBITE) (English) MICHAEL ELISEEFF, TOURIST, SAYING: " Being near the sharks, having them close to the boat, so that was the best part for me. Seeing them for the first time. Diving in Oslob for the first time as well. It was really good." (SOUNDBITE) (English) SANDRA KOWALCYKZ, TOURIST, SAYING: "I've seen the local people how they feed the whale sharks, and I think its good for them, they dont suffer here" The villagers along this stretch of coast say they're aware of the importance of balance between sustainability and development, but as the money flows in, the argument for changing the status quo becomes harder to make.