MANILA (AFP) - Environmentalists have hit out at organisers of the Miss Universe beauty pageant in the Philippines, calling them "irresponsible" for letting contestants swim with endangered whale sharks.

A group of bikini-clad Miss Universe candidates were photographed smiling and waving from boats on their way to swim with the world's largest living fish in waters off the island of Cebu on Tuesday (Dec 13), ahead of January's contest.

Tourists swimming with the creatures is strongly discouraged by environmental groups, who say feeding whale sharks makes them dependent and also leaves them vulnerable to poaching or injuries from boat propellers.

"We are afraid because with Miss Universe going there, the Philippines is promoting a bad tourism practice," Vince Cinches of Greenpeace Southeast Asia said.

"We are telling the world it's okay to do this, aggravating this kind of behaviour." The Philippines is hosting Miss Universe next year and the tourism department said the trip was part of an inspection of potential competition sites.

The whale shark visit was coordinated with the help of the local municipality "which promised a well managed marine interaction experience", tourism undersecretary Kat De Castro said.

Wildlife conservation groups in the Philippines have for years opposed whale shark tourism in Cebu's Oslob city, but local officials say the practice is a source of livelihood for the community.

Marine Wildlife Watch of the Philippines opposes this.

"It's irresponsible and unsustainable. It's not even ecotourism. You sacrifice the environment just for a selfie," the group's director AA Yaptinchay said.

A veterinarian and aquatic ecologist, Yaptinchay urged the government to enforce guidelines including maintaining a three-metre distance from the whale sharks and prohibiting swimmers from touching them.

Internet users in the social media-obsessed nation expressed outrage online.

Besides environmental issues, security has been a concern for the Miss Universe competition.

In August, the authorities said they were looking into a "serious" threat by an Islamic State in Iraq and Syria-related group to bomb the pageant.