A humble dive tank saved a paua diver from being "sliced in half" during a violent shark attack off the Chatham Islands.
The diver was near Pitt Island when he was hit side-on by the great white and dragged seven or eight metres while being thrown about the water.
He later found a tooth stuck in the buckle of his mangled backpack, signalling what might have been.
"His harness and backpack were sliced to pieces," Paua Industry Council chief executive Jeremy Cooper said.
The shark "shook the hell out of" the terrified diver as it threw him around, but he was saved by the tank, Cooper said.
"He said he was looking out for blood in the water, because that's what he was worried about."
It was the second time the victim had been attacked by a shark, following an earlier attack in the early 1990s in which his foot was bitten, according to Department of Conservation (Doc) marine scientist Clinton Duffy.
However, shark attacks near the Chatham Islands were rare, with the last one occurring in 2005 when a paua diver lost an arm, Duffy said.
Before that, a paua diver was "almost bitten in half" in 1993.
There had been an average of about two shark attacks a year around mainland New Zealand in the past 20 years.
Niwa principal scientist Dr Malcolm Francis said the waters off Chatham Islands were a popular spot for great whites.
Research conducted between 2005 and 2008 tagged 10 sharks in the area, but there were likely to be many more.
They were most commonly found between February and July.
"In winter the sharks mostly emigrate to the tropics north of New Zealand, places like Tonga, Fiji, New Caledonia, Great Barrier Reef. Some juveniles remain in New Zealand year-round, but most adults or sub-adults emigrate."
Great whites typically started hunting larger marine mammals such as seals and dolphins once they grew to about 3 metres in length, and that is when they were a risk to humans, Francis said.
They hung around New Zealand for about five months a year, and in the tropics the rest of the year.
A 2018 report conducted by New Zealand and Australian scientists estimated there were about 5500 great white sharks in the area covering eastern Australia, the Pacific Islands, and New Zealand.
Cooper said paua divers obtained approval about five years ago to wear dive tanks. That meant they could remain on the water floor instead of coming up every 45 seconds or so, making them less obvious to sharks.
The diver has been approached for comment.
The incident had not been reported to Niwa or Doc.
