At first glance it looks like a vicious attack as a diver finds her leg clamped in the jaws of a beluga whale.

In fact, the animal was rescuing diver Yang Yun (26) as she floundered during a free diving competition in a tank more than 20ft deep at Polar Land in Harbin, North East China.

The diver made the plunge without diving equipment among the whales in a tank that had been chilled to Arctic temperatures but found her legs crippled by cramp from the freezing cold.

At this point Mila the beluga surged to the rescue, pushing the striken diver back to the surface.

Officials said the diver owed her life to Mila, who works closely with humans.

“We suddenly saw the girl being pushed to the top of the pool with her leg in Mila’s mouth,” one official said.

“She’s a sensitive animal who works closely with humans and I think this girl owes Mila her life.”

At depths of more than 20ft, water pressure keeps a human body down, particularly if the limbs are paralysed by the cold, as in this case.

Yang Yun was left uninjured after her ordeal as belugas, which live in Arctic and sub-Arctic waters, are equipped with only small teeth.

“I began to choke and sank even lower and I thought that was it for me — I was dead,” Yang Yun said.

“Until I felt this incredible force under me driving me to the surface.”