"Though she's been right into the surf zone at Shipwreck Bay at least once," he said. Yesterday morning the shark was 1km off Tauroa Pt.
Mr Duffy said even a juvenile great white could be dangerous so people should exercise common sense about where they swam, surfed and dived.
"However, given how common they are around the upper North Island, attacks on people are very rare."
Surfers and swimmers enjoying Shipwreck Bay/Te Kohanga yesterday were unfazed about sharing the water with a great white. Aucklander Hamish Don said sharks were incredible animals.
"There's a resident shark at Henderson Bay that doesn't bother people. They're probably too well fed up here to be a worry," he said.
On the same day Mr Duffy saw eight great whites, Kerikeri electrician Barry Jordan was on a family fishing trip when he hooked something big in 90m of water off Nine Pin Rock in the Bay of Islands.
The experienced game fisher was live-baiting for marlin when a shark took the bait instead and "went airborne". It took half an hour to bring it alongside the boat where it broke free.
"I had my hands a bit full to take a photo but I got a pretty good look at it. It was definitely a great white."
Mr Jordan put its length at 3.5-4m and its weight at 400kg. The same week a spearfisher told him he had been forced out of the water near Hole in the Rock by a great white with the same kind of tag attached to its flank.
Mr Jordan said he had caught plenty of sharks before "but nothing like this".
Mr Duffy said Mr Jordan's description of the tag had allowed him to trace it to the Neptune Islands off the South Australian coast, where it had been tagged in 2011. Great whites were known to travel frequently between New Zealand and Australia's east coast, but not from South Australia. That made the Kerikeri sparkie's catch unusual.
The only other New Zealand sighting of a great white from South Australia was in 2002 when one was caught in a gill net at Ahipara. Meanwhile, last month's sighting of so many juvenile great whites in the Kaipara Harbour lends weight to the theory that the upper North Island is a breeding area and nursery. The Kaipara sharks measured 1.8m to 3.4m long; adult males grow to a maximum of about 5.5m and females possibly as long as 7m.
The distinctive markings on great whites mean that individual animals can be easily identified from sightings or photos. Anyone with photos of great whites, even if taken years ago, is welcome to send them to cduffy@doc.govt.nz to aid Mr Duffy's research.
Other sightings last month include a 4.5m great white in the Waitemata Harbour and one "as big as a tractor" leaping from the water at Leigh.
The last death in New Zealand waters from a great white was that of filmmaker Adam Strange in 2013, about 200m off Muriwai Beach. It is believed he was swimming through a school of fish, in an area where people had recently been fishing, when he was attacked.
