SWIMMERS might think twice about cooling off in these waters, which became a spectacular battleground when a group of orca whales attacked a school of sharks.

The sharks had been swimming close to the shore on Boxing Day at the Blue Cliffs Beach in Tuatapere, New Zealand as the orcas - also known as killer whales - stalked them through the sea.

Moments later the hungry whales sent the feared fish scattering through the waves as they sprung their assault, the Daily Mail reports.

In a spectacular display of natural predators at work, the whales herded the sharks towards the shore to force them into shallow waters.

One shark, desperate to escape from the enormous beasts, even beaches itself on the sand. It is seen desperately flapping around in a bid to escape the whales, which were unable to move onto the sand.

The incredible feeding frenzy was captured on film by residents who said they had never seen a display of such aggression from the orcas.

As witnesses gathered on the shore, one plucky dog couldn't resist trying to get involved and can be seen approaching the stranded shark before barking at it.

Eyewitness David Evans said he was told there were whales in the area and raced to the beach to record the spectacle.

"We all piled in the truck and grabbed a camera, grabbed the video and went down to the beach and just started shooting," Mr Evans told 3News in New Zealand.

It is thought that there were around six whales and six sharks in the water. Although one of the sharks had a nasty gash to its side, it's not known if the whales managed to catch their dinner.

"That particular [injured] shark had been beaten up by the orcas," resident Tracy Thomas told stuff.co.nz.

"There were heaps of sharks just off the beach, swimming in towards the beach then turning around and going back out."

Peter Robertson said his dog, Flea, had gone into the water when it became excited by what was happening.

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

Orcas are significantly stronger, faster, heavier and larger than even the most ferocious of sea beasts - the great white shark.

It is not known what species the attacked sharks were. However, they were much smaller than the orcas and would have come off worse in most clashes.

Orcas feed on seals, sea lions, large fish and sharks - although it is rare to see such a aggressive display of hunting so close to the shore.

However, the hunting tactics and prey species vary between different pods of orcas.

Jim Fyfe, a marine ranger at the Department of Conservation Otago office, said that sharks are "well within the range" of orcas.

Originally published as Killer whales take on sharks in death match