WASHED UP: A bloodied shark washed ashore on Blue Cliffs Beach as orcas just off the coast hunted on Boxing Day.

Boxing Day at Blue Cliffs Beach, near Tuatapere in Southland, turned into a feeding frenzy, as a pod of orcas and a group of sharks clashed in the surf.

Eyewitness Tracy Thomas said it looked like the orcas, also known as killer whales, were hunting the sharks, with one wounded shark washing ashore with a bloody gash on its snout.

"That particular shark had been beaten up by the orcas," she said. "There were heaps of sharks just off the beach, swimming in towards the beach then turning around and going back out."

TRACY THOMAS BLISSFULLY UNAWARE: Pig dog Flea plays in the water at Blue Cliffs Beach, unfazed by the shark behind him.

Longtime Blue Cliffs Beach resident Peter Robertson said he had never seen sharks and orcas behaving as they did off the beach.

"It would appear the whales were fighting the sharks ... the sharks were coming ashore because they didn't want to be in the water."

Off a small section of beach, there were at least six orcas and six or more sharks, he said.

TRACY THOMAS ON A MISSION: An orca prowls off Blue Cliffs Beach on Boxing Day.

Flea, a dog Mr Robertson was looking after over Christmas, enjoyed running around in the water, unafraid of the sharks.

"It was a bit of fun [for Flea], They were making a bit of a splash in the water," Mr Robertson said.

"The pig dog was down there going into the water. It looked like it was rounding them up," Mrs Thomas said.

The shark which washed up on the beach later disappeared after high tide. "It could be a whale's dinner by now."

Jim Fyfe, a marine ranger at the Department of Conservation Otago office, said small sharks were sometimes hunted by orcas.

"Sharks are well within their range as a prey species."

He said it was possible the pod was one seen off the coast near Dunedin earlier this month, but that could not be confirmed.

Separate pods and larger groups of orcas often have different hunting tactics and prey species.

The orcas seen off the coast of Otago habitually seemed to feed on seals, while North Island orcas enjoying rounding up and feasting on stingrays, Mr Fyfe said.