Reporter: Peter Overton
Producer: Nick Greenaway
Here's some chilling news. Just what you want to hear as you head back to the beach this summer.
Sharks are not only deadly, they're smart, too. And the one we fear most, The Great White, is the smartest of them all.
That's what the experts are telling us, based on the latest research into the predator's brain and its thought patterns.
That's right, they can think. Great Whites aren't just mindless killers, they're tacticians that actually plan their attacks.
But as Peter Overton tells us, when you get up close to these monsters, you don't need a science degree to know why they're called the ultimate assassins.
IAN GORDON: On your right, on your right, on your right! Where did that one come from?
PETER OVERTON: I'd always thought they were mindless killers.
IAN GORDON: No matter where you look they're always coming from behind you. And they're so big close-up.
PETER OVERTON: And my first moments in this cage do nothing to dispel that idea.
IAN GORDON: Oh, he's hit the cage! He's hit the cage!
PETER OVERTON: The tail, wow, what a hit. We're at the Neptune Islands off Port Lincoln in South Australia where the great whites come to hunt seals.
IAN GORDON: When they mean business, they mean business, there's no doubt about that.
PETER OVERTON: But despite their menacing appearance my diving partner, shark researcher Ian Gordon, has assured me I'm safe, I'm not lunch, they're simply checking me out. Wow, what an amazing experience, you can reach out and touch them they're that close to you, you can see their teeth, their extraordinary eyes, it really is a privilege to be that close to these kings of the ocean.
IAN GORDON: They're just such amazing animals. Every time we think we look like were starting to find out something about them we realise that we know nothing and we have to learn more.
PETER OVERTON: According to Ian Gordon, until now, our thinking about Great White Sharks has been skewed by our fear of them, a fear which has created countless myths. But on this journey, I'm about to see them in a whole new light... ..to find out just how sophisticated they really are. How their bodies are perfectly engineered, and how their intelligence and a mysterious sixth sense makes them such ferocious predators.
IAN GORDON: White sharks are like assassins. They have to learn how to be able to understand what their prey is doing to be able to effectively catch them.
PETER OVERTON: So you're saying they're smart?
IAN GORDON: They're smart, yeah. DR
KARA YOPEK: So what we've got here is the brain of a great white shark.
PETER OVERTON: So much smaller than I thought. DR
KARA YOPEK: I know, it's pretty awesome, though, that something that small can do all those really complex behaviours.
PETER OVERTON: It's only now that researchers like Dr Kara Yopek are starting to piece together a picture of just how complex their behaviour really is. DR
KARA YOPEK: We've finally got through to the brain and it's really, really interesting.
PETER OVERTON: For a start, great whites actually do think. So what you're saying is a great white thinks about its prey and what strategies to use when it attacks. DR
KARA YOPEK: I mean it calculates things like risk, and so there is a fair amount of risk involved because they're hunting prey that could potentially hurt them so it does have to calculate the risk involved, it has to calculate how to catch its prey because, I mean, what does a shark need to do to survive? Needs to, I guess, eat and mate.
PETER OVERTON: Nowhere is their ability to plan attacks better illustrated than at the seal colonies off the South African coast. Here, the great whites have learned how to stalk and surprise their prey - charging vertically up from the depths to seize unsuspecting seals. DR
KARA YOPEK: I think they're amazingly intelligent animals. They're just really tuned in to how they need to survive best in that environment and be really, really successful.
PETER OVERTON: As well as thinking, the key to the great whites' success as a predator is its extraordinary agility and speed controlled by this part of the brain called the cerebellum. So, quite complex behaviour and strategies. DR
KARA YOPEK: Complex mode of behaviour is what I'd say, yeah.
PETER OVERTON: Great whites combine all their physical prowess in a whole range of hunting tactics including what's called 'spy-hopping' - they actually stick their heads out of the water to have a better look around. DR
KARA YOPEK: They can perform an amazing repertoire of behaviours. Their sense of vision is really acute and they clearly use it in a very interesting way by popping their heads out of the water.
PETER OVERTON: That's pretty sophisticated isn't it? DR
KARA YOPEK: I think it's amazing. I think they're amazingly smart to have come this far and to have adapted these skills is just absolutely... it really blows me away personally.
PETER OVERTON: The great whites' formidable arsenal includes the ultimate underwater tracking system - a maze of super sensitive pores on their faces that give them a sixth sense - the ability to detect prey kilometres away. DR
KARA YOPEK: A heartbeat is going to send off electrical signals and the shark can pick that up which is absolutely an unbelievable thing for it to be able to do. A tiny dipole, sending off an electrical impulse, and it can sense that and follow it back to that item.
JAKE HERON: You can see where he has bitten through the board, he has bitten it 'cleanly', I guess the word is.
PETER OVERTON: You can really see the teeth marks of the shark can't you. Very, very clear.
JAKE HERON: Yeah, you can see the individual marks right along here - each separate tooth. They were pretty big teeth.
PETER OVERTON: For all their impressive weaponry, great white sharks can also be remarkably cautious creatures - they often taste before they dine. which explains why some people, like Jake Heron, survive their terrifying encounters.
JAKE HERON: I was actually paddling at the time and I've been struck from underneath and knocked off my board to the left but it has hit me at great force from underneath.
PETER OVERTON: Jake's attack, while surfing near Port Lincoln, shows how a great white's intelligence can override its basic instinct to kill. The 4-metre shark smashed into Jake at a speed approaching 40km/hour.
JAKE HERON: That's when I've looked back and I've seen I've seen the tail and it's really thrashing, and the dorsal fin, and the shark has spun around and I've been sitting on its actual pectoral fin and at that stage I started punching it because it was very close and even kicking it because I was sitting on it so I was punching it as hard as I could and kicking it.
PETER OVERTON: In the frenzy the shark took a bite out of the surfboard and swam off. But Jake, still attached to the board by his leg rope, was dragged through the water. That must have just been terrifying.
JAKE HERON: Yeah, yeah it was. Well I knew what was happening, I knew the shark had bitten the board and was pulling it along so I knew exactly what was going on, I was just, you know, "What next?"
PETER OVERTON: But then something remarkable happened - the shark literally had second thoughts. Fearing Jake's violent defence could mean he was a serious threat, it called off the attack. He was left with deep cuts to his right arm and right leg, but alive.
JAKE HERON: Yeah, I'm just glad or lucky, whichever way you wanna put it, that this bite, this massive bite, wasn't on me because I think if it had bitten me the same way it bit my board it would have been a different story, you know, it would have been all over.
PETER OVERTON: There's no reason to say it couldn't have got you there.
DR STEPHEN WROE: You've got to admire the purity of the design. In terms of biology and engineering it's an exquisite construction.
PETER OVERTON: It really excites you when you talk about these creatures, doesn't' it.
DR STEPHEN WROE: It's a bit sick, maybe, huh?
PETER OVERTON: More than anyone, scientist Dr Stephen Wroe can tell Jake Heron just how lucky he was to survive his encounter with this ultimate killing machine. From to the supreme engineering of their jaws, to the piston-like muscles in their tails he is in awe of the great white's exquisite design.
DR STEPHEN WROE: This is a design that has been honed and improved on incrementally over millions of years. This is a design that works.
PETER OVERTON: The jaws and the teeth are an engineering marvel?
DR STEPHEN WROE: It's amazingly sophisticated. It's a very, very complex system.
PETER OVERTON: Dr Wroe is using advanced computer software to determine the bite force of great whites. It's world-first research and his results are clear and terrifying.
DR STEPHEN WROE: For this guy, which is a juvenile sub adult, we have a bite-force estimate of about 220 kilograms, which is a lot. But for the largest, my predictions would be well over a tonne. So about 1,100 kilograms. Among animals I've looked at that certainly would make it the biggest biter on the planet. To put that in perspective, another way of looking at it is a really big African lion would bite with about 300 kilos. As the jaws open the gums basically pull those teeth teeth out. So the teeth flick out, okay. You don't see it in a fixed dry specimen like this. But if you look at a wet specimen, bang. You know so you've got 300 flick blades here, bang.
PETER OVERTON: Now, if we haven't frightened you enough, there's one more scary fact you should know about great whites. They can turn up anywhere - from the coastal shallows to the middle of the oceans. Apart from everything else, great whites are like submarines - their giant livers act as buoyancy tanks. They can even control their body temperature at great depth - all of which gives them an enormous range, chillingly shown in this home video. These tourists were swimming off the back of boats, 3,000 kilometres off the South American coast when out of nowhere a great white appeared. Heather Boswell survived, but only just, after the 4-metre shark took her leg.
IAN GORDON: We as humans are only occasional visitors to the ocean and if we go in there we have to take the risk of going into a wild environment that we can't control.
PETER OVERTON: So you have to wear the consequences?
IAN GORDON: Yes, we have to wear the consequences.
PETER OVERTON: Which brings us back to the Neptune Islands near Port Lincoln. Ian Gordon has been known to dive in these parts without the cage but I'm not so sure. Their eyes, you feel like they're watching you all the time. After all I've learnt, even if these sharks aren't mindless killers, they're still big with row upon row of serrated teeth and not forgetting their bone-crushing jaws. I think it's perhaps better for me to admire them from behind bars. You've jumped out of the cage and swum with them, though. I mean is that the most stupid thing you've ever done?
IAN GORDON: My parents think so.
PETER OVERTON: Yet to me, these animals terrify me, and I think they do most Australians.
IAN GORDON: The whole shark thing and the fear thing is... it can eat you alive and that's not within our consciousness here in Australia, having to deal with animals that can eat you alive.
PETER OVERTON: The ultimate assassin?
IAN GORDON: The ultimate assassin, yeah.