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In the warm waters of the Far North, the hunter has become the hunted.

A government expert is tracking down the real-life Jaws - great white sharks that he believes are prowling just offshore.

With summer in full swing and many of us flocking to the beach, he says Kiwis who take a cooling dip in the ocean may find themselves swimming alongside a shark.

Clinton Duffy, a shark expert from the Department of Conservation, said there were warning signs that you may look like a tasty dinner.

"A shark that's constantly circling you, seems agitated, swaying its head from side to side ... If it starts bumping you it's a sign that you might be edible," he said. "You should probably get out of the water then."

Duffy is combing the waters of the Far North in search of juvenile great whites - the man-eating shark infamous for its starring role in Steven Spielberg's 1975 hit movie.

Three days of aerial and sea searches in Northland last week sighted bronze-whaler sharks but no great whites.

Commercial fishermen in the area have told Duffy that February is the month for great white sightings.

Duffy, a self-described "passionate" shark fan, said the feared fish was commonly found 200m to 300m from the shore, in river mouths and in harbours. He said people's fear of sharks was "largely unfounded."

"Sharks are continually getting a bad rap," he insisted.

"In most circumstances sharks can't even recognise humans in the water."

However, Duffy has some advice for anyone who spots a shark and is worried about its intentions.

"Most people realise if you get into the water, you're in the shark's territory," he said.

"If you don't know what species of shark you're looking at, the best advice is to get out of the water quickly and calmly.

Duffy has had a few close encounters with aggressive sharks. He once gave a blue shark a "sound whack on the snout" to deter it from advancing on him.

The last recorded fatal shark attack in New Zealand waters was in 1976.

Duffy intends to electronically tag any great whites he finds this summer to learn more about their living habits. A transponder inserted by spear near the shark's dorsal fin is linked to a satellite.

In three years of research, he has tagged 13 great whites around New Zealand.