Fast shark facts:
• Huge great white sharks congregate around Stewart Island in late summer to feed on seals.
• Famed shark expert Jeff Kurr believes they are among the largest anywhere on earth.
• Kurr and his team caged dived with the sharks and found them to be very aggressive.
• Despite research making gains in the past few years, very little is known about New Zealand's great white shark population.
Tale of a monster shark:
It's pitch black and Kina Scollay is in a cage at the bottom of the ocean as huge shapes emerge from the darkness.
The world's apex predator, the great white shark, is here in numbers. And it's hungry.
This is not off the coast of South Africa or Australia but in the waters around New Zealand's South Island. But Scollay and his documentary team aren't here for large numbers of sharks. They are here for one mega-shark.
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Local fishermen have been telling tales of a shark larger than a boat, some say up to 9.4m, just off Stewart Island.
Scollay, a Picton-based shark researcher and cameraman, teamed up with a documentary crew from the Discovery Channel to uncover the truth in the legend.
The crew, led by famed American shark expert Jeff Kurr, scoured the region's known shark spots.
It quickly became apparent that they were most active at night so Scollay and cinematographer Andy Casagrande took up the daunting challenge of cage diving in the dark.
"You're in a cage at the bottom of the ocean a fair way down in the middle of the night," he tells the Herald on Sunday. "It's black - completely black - except for our own lights and you've got a bunch of extremely aggressive sharks."
"These things are just coming out of the darkness and they're super-big ... there were quite a number of sharks there and they were all go." The sharks, some more than 5.5m long, repeatedly rammed the cage, moving it across the sea floor.
"It's one of the most full-on shark-filming dives I've ever had, hands down," Scollay says.
"You've got these massive creatures rushing at you and from the time they're visible to the time they're on top of you is a fraction of a second. You're talking about a very large predator that eats things for a living."
Kurr, who has been part of the Discovery Channel's immensely popular Shark Week series since 1991, believes New Zealand's little-known great white shark population includes some of the biggest in the world.
"I spoke with a lot of fishermen and locals about what sharks are up to in the area," he says. "Many of them were telling me about a huge shark they would see on occasion. One man even stated he felt it was well over 30 feet long [9.4m].
"We wanted to come out and see what was going on in these waters and whether it was true or just a legend. The best way to do that is to go down in our cages and look around."
Jeff Kurr, Andy Casagrande and Kina Scollay feature in Lair of the Mega Shark.
Despite weighing up to 2.5 tonnes, great white sharks can reach speeds of 56km/h. They have rows of razor-sharp teeth behind the main ones, ready to replace any that break off. Females grow larger than the males, reaching lengths of about 7min total to the males' 5.5m.
There have been reports of sharks of a whopping 11m but none have been formally documented. However, experts are quick to point out our fascination owes more to Jaws movies than to any real threat. The death of Adam Strange in a great white attack at Muriwai in February last year was the first in New Zealand waters since 1976.
The sharks are classified as a vulnerable species and have been protected in New Zealand waters since 2007.
The documentary team's hunt - Lair of the Mega Shark - kicks off Shark Week at 8.30pm on December 1 on the Discovery Channel.
Kurr says they found a population of very large, sexually mature male sharks around Foveaux Strait.
"It was quite spectacular. I think the sharks we saw in New Zealand were probably the largest sharks I've ever seen in 25 years of Shark Week," he says.
"It just intrigued me that here's an area on the southern tip of New Zealand that is fairly remote and not a tonne of research has been done there."
One of the sharks they came across was between 6 and 7m. "It was a big, big animal. And just a beautiful, majestic animal, a shark that you think might be 50 or 60 years old.
"It was a one-of-a-kind creature."
There is still a lot more to learn about great whites.
Kurr says during his time in New Zealand, his team was able to use cutting-edge technology, including a "fin-cam" - a camera clipped to a shark's dorsal fin, providing insights into its behaviour.
It revealed great whites are more social than previously thought, not the solitary killers they are sometimes portrayed as, Kurr says.
"We saw the shark interacting with other sharks. He would use body language to communicate with them."
Although they didn't find a shark as large as the legend, Kurr says he wouldn't be surprised if one is out there and says sharks they saw came close.
Scollay says although the great white research project has made huge gains in the past seven or eight years in understanding great whites, there is still much more to learn.
He has been working with sharks for years and says he discovers more on every dive. "We still have a lot to learn about the distribution of great whites around New Zealand.
"In New Zealand if you want to see a great white you go to Stewart Island because we know there is an aggregation of great whites there from around autumn into winter.
"The Chatham Islands is another place where there are aggregations of sharks but that's not to say that's where all the great whites go in New Zealand at that time of year."
• Discovery Channel's Shark Week starts Monday, December 1, from 8.30pm.
How to stun a shark (don't try at home):
A still from Zombie Sharks.
They are one of the planet's deadliest predators but great whites have a weakness.
When turned on their backs they go into a trance-like state - known as "tonic immobility"- becoming easy prey for orca.
And, in a move treading the divide between bravery and foolhardiness, shark diver Eli Martinez has gone head-to-head with a great white and tried to flip it belly-up.
Tonic immobility has been studied by scientists for years, but a recent spike in orca attacks on great whites suggests orcas have learned to immobilise the huge predators.
Reports of New Zealand orcas using the technique on sharks and stingrays led Martinez to these shores where he tried to use it.
In his Discovery Channel documentary Zombie Sharks, Martinez flips a large tiger shark and balances it on his hand. But his attempt to use the technique on great whites off Stewart Island was less successful.
He manages to lay a hand on a 4.9m, one-tonne great white and begin to lift it, which made it go "kind of loopy".
"You can definitely see that there is a potential for [tonic immobility in great white sharks]."
Marine biologist Ingrid Visser, New Zealand's expert on orcas, also appears in the documentary to give her account of orcas using the technique.
"They definitely use tonic immobility and if you look at any photographs you can find of orca carrying sharks the shark is normally upside down."
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