SARAH FERGUSON, PRESENTER: Hello and welcome to Four Corners. I'm Sarah Ferguson.

Few things trigger a more primal fear in us than the thought of being eaten by a wild animal. Yet it's a chance millions of Australians take when we go to the beach for a swim or a surf.

The risk is small but the number of shark attacks in Australia has doubled since the 1980s. In the past five years there have been 84 shark attacks, 12 of them fatal.

Tomorrow marks a grisly anniversary: a year since Tadashi Nakahara was mauled by a great white in the surf at Ballina on the New South Wales north coast: the beginning of a cluster of nine attacks, one fatal, in that part of Australia in a year.

A similar cluster occurred in Western Australia, where seven people were killed between 2010 and 2013.

Tonight we'll look at why those deadly clusters occur and hear from scientists who question whether nets and drum lines on our swimming beaches actually safer.

Geoff Thompson begins his investigation in the water off Sydney's Bondi Beach.

(Footage of Bondi Beach, showing surfers, beach dwellers, lifeguards and swimmers)

GEOFF THOMPSON, REPORTER: A perfect summer's day on Sydney's Bondi Beach. Swimmers, surfers and families bask in our national birthright to enjoy our beaches without fear.

We feel safe here at Bondi Beach because we're under the ever-vigilant gaze of the world's most famous lifeguards and because a few hundred metres offshore there are nets which, we are led to believe, protect us from sharks.

(Footage of Geoff Thompson underwater, inspecting shark net at Bondi Beach)

Below the surface is another story.

At 51 New South Wales beaches nets like these trap sharks and other sea creatures.

They're only 150 metres long and wide open at the top.

BARRY BRUCE, SENIOR SHARK SCIENTIST, CSIRO: There's still this misconception that the shark net is a barrier. It's not: it's a fishing device.

It's, it's a couple of hundred metres long. There might be two at a beach which is many, many kilometres long.

They are set at a depth offshore where they don't reach to the surface, so they only come up six metres or so from the bottom in 10 metres of water.

In some respects you have to be an unlucky shark to get caught.

GEOFF THOMPSON: Today no sharks were caught. Government contractors arrived in time to set three stingrays free.

BARRY BRUCE: Shark nets at Bondi Beach have caught white sharks and if you're dead you can't bite anybody. What we don't know is whether that shark would have ever bitten anybody and we don't know how many sharks swam through the area that didn't get caught.

(Footage of MV Calypso Star II approaching Neptune Islands. Geoff Thompson is onboard)

GEOFF THOMPSON: Australia's most feared sharks are great whites, responsible for more fatal attacks than any other species.

With its tens of thousands of seals, the Neptune Islands in South Australia are a great white hunting ground.

(Footage of MV Calypso Star II crew preparing shark cage)

CREW MEMBER: One just here.

CREW MEMBER: Shark!

ANDREW WRIGHT, SKIPPER, MV CALYPSO STAR II: Shark. There it is. There's a white.

ONLOOKER 1: Oh, gee. That's a monster.

ONLOOKER 2: Wow. It's huge.

ANDREW WRIGHT: You don't have to worry about your moustache, but you will have to worry about your friends.

GEOFF THOMPSON: I came down to see the animals for myself.

ANDREW WRIGHT: Please keep your arms inside the cage. They're not cute and cuddly. They are a wild animal - and that's a pretty bloody big one, too.

GEOFF THOMPSON: Scientists estimate that there are about 1,700 of them around Australia's coast.

Our boat had barely stopped before they were circling.

The thought of getting in there's a bit terrifying, actually (laughs). They're definitely attracted to the boat.

ANDREW WRIGHT: If you need to come to the surface, a good foot of the cage sticks above the water. When the cage is in, it's going to be sitting in the water, floating independently to the boat, but it will be held against the boat with a couple of nice, heavy ropes so the old shark can't bite through it.

We'll get the cage in the water and get this first group of divers in.

Spin around on the ladder and face us.

GEOFF THOMPSON: The sharks can't resist the lure of chunks of tuna guts tossed out on the end of ropes.

(A bucket of chum is thrown out into the water. A shark approaches and thrashes against the cage)

GEOFF THOMPSON: Now I'll get to see one of these white sharks up close.

(Geoff Thompson dons scuba gear and climbs into the shark cage. Underwater, several sharks and smaller fish circle the boat. A shark swims up to the cage and bites at the outside)

GEOFF THOMPSON: Look at that! Wow!

That was amazing. They love to attack from below, attacking prey sitting on the surface - which is exactly where swimmers and surfers are.

Magnificent creatures. I've never really felt quite so small and vulnerable and insignificant as I do right now.

(Geoff Thompson climbs out of the cage onto the boat and removes his helmet)

GEOFF THOMPSON: Wow. Amazing creatures. I wouldn't want to meet one in the surf.

(Footage ends)

BARRY BRUCE: Most of the time when sharks and people are in the same proximity with each other, sharks don't bite people.

And this is one of the real challenges in understanding shark attack, because we're looking at the exception rather than n- what normally happens. There will be a relationship between the number of attacks and the numbers of sharks, but it's, it's not a straightforward relationship. You can have areas where there are a lot of sharks and no attacks. You can have areas where there are very few sharks and an attack.

We bubble oxygen, oxygenated water through the gills to keep them calm.

GEOFF THOMPSON: Barry Bruce is the CSIRO's top great white expert.

(Barry shows Geoff a map of Australia, with recorded shark routes marked)

BARRY BRUCE: As you can see, white sharks travel extensively across their Australian range and including across the Tasman Sea to New Zealand.

GEOFF THOMPSON: The tagging of great whites has revealed they have two distinct populations.

BARRY BRUCE: The sharks we tagged in Eastern Australia generally stayed in eastern Australia or went to New Zealand and back. And the sharks we tagged west of Bass Strait - in South Australia and Western Australia - tended to move through Western Australian and South Australian waters.

So it appears that Bass Strait was almost a barrier.

That's about the northern range of, of white sharks in Australian waters.

GEOFF THOMPSON: Tagging also shows a concentration of young great whites off the coast of Port Stephens in NSW.

BARRY BRUCE: It's a nursery area for white sharks and it's quite geographically discreet. It-it's only on a few beaches. And if you've swim at those beaches you would have swim with white sharks.

Interestingly, on those particular coastal beaches there haven't been an attack. There's been attacks around that area, but not on the beaches where the sharks spend most of their time.

GEOFF THOMPSON: Further up the NSW north coast there was a cluster of shark attacks last year.

(Footage of Geoff alighting an aeroplane at Ballina Airport)

Close to Australia's easternmost point, the beach town of Ballina has been in the grip of intense shark fear. I came here to get a taste of it.

There were nine shark attacks in the area last year and one of those was fatal.

(Footage of boardriders' club members setting up for competition meeting)

Don Munro is the president of the local boardriders' club. Today is the first competition since Ballina's last shark attack.

GEOFF THOMPSON: You're not having these events as much as usual, so what's the, what's the feeling?

DON MUNRO, PRESIDENT, LENNOX-BALLINA BOARDRIDERS CLUB: Um, well, the feeling is, um, we've got to be on red alert to, to ensure that, ah, the guys that are in the water, um, are gonna be safe in the water.

Ah, we've, ah, we've had a situation today where we have called them in. Um, it did look like we'd spotted a shark or two.

JASON ATHERTON, SURFER: I mean, it's always in the back of your mind but you, you try not to think about it.

TOBY RADCLIFFE, SURFER: It's like there's two, there's two ways of thinking about it: either completely ignore it or let it completely consume you, you know. And like, s- and then there's examples of both so it's...

GEOFF THOMPSON: Yeah, but, but surfing's always like that, right? It's always slightly in the back of your mind when you're surfing?

TOBY RADCLIFFE: Yeah but no, it never really was.

GEOFF THOMPSON: Yeah, right.

TOBY RADCLIFFE: You know, like, you'd paddle out, you know, in dirty water on dark and not even think about it.

And now you kind of really weigh up: "Hey, is the surf that good for me to lose a leg?" Um, if it's pumpin': yeah, well it is worth it.

GEOFF THOMPSON: You've got a lot of dolphins around that surfer. He's lookin' a bit nervous?

DON MUNRO: Yeah, well, that's right. Yeah. A-th... A huge pod of dolphins there. That's - they're bigger th- that's a bigger pod than we normally would see, in-intermixed with them could have been sharks, so, um...

It's, I'd say, highly unlikely that there's not a shark or sharks out there.

GEOFF THOMPSON: Yeah. Are you worried about the sharks? Are you worried about the sharks and the kids?

CHILD: No.

DAVE MCINNES, SURFER: Oh, yeah, a little bit. We just try and be sensible about it. You know, like, obviously a lot of eyes on the beach, keeping an eye on it.

We've got a lot of choppers going over, so that always makes us feel a little bit, you know, safe. You look for diving fish. And as I said, we just try and be sensible about it.

You know, like, that's all you can really do and, you know, we don't wanna stop surfing. We don't want the sharks to stop us from doing what we love.

So, you know, we're just trying to get on with it as, as best we can and as safely as, as possible as well.

(Geoff Thompson and Darren Rogers look at several local newspapers carrying headlines of shark attacks)

DARREN ROGERS: Tadashi was taken in February, which is the middle of summer.

GEOFF THOMPSON: And that's when it started, really?

DARREN ROGERS: That's when it started. And it, and it picked up pace, you know. There was sighting after sighting. Um...

GEOFF THOMPSON: Darren Rogers is struggling to get past his experience of a fatal attack in Ballina one year ago.

He helped pull Tadashi Nakahara from the water after the surfer was mortally mauled by a great white shark.

DARREN ROGERS: Um, these are all, all about Tadashi; um, when they closed the beach. It's all buried in here, um... And of course every time there's a new attack, the first thing they mention - well, straight after it - is that in February 9, Tadashi Nakahara was fatally attacked at Shelly Beach.

GEOFF THOMPSON: Darren's barely surfed since the attack.

DARREN ROGERS: And It's still hard - very hard - for me tell the story. But the thing that is the most, um... is his eyes, for me. Um, I can't forget his eyes and they're the things that, that, just... I just see his eyes all the time.

GEOFF THOMPSON: He gave a dying Tadashi CPR.

(To Darren) Is it something to do with the fact that, for you, surfing was synonymous with life?

DARREN ROGERS: Yes.

GEOFF THOMPSON: And then suddenly surfing became synonymous with death?

DARREN ROGERS: Yeah, and m- even more than death: w-with h- with horror. Um, absolute horror.

And that's my favourite beach as well. And it was a perfect day: beautiful day, clear water, February.

(Footage of Surf Life Saving Far North Coast vehicles off coast of Ballina: personal water craft, helicopter, jet boat)

GEOFF THOMPSON: Few have seen more of what shark bites can do to human bodies than Ballina's surf lifesavers.

Tadashi Nakahara was beyond saving.

But the rapid response of these men, working with a rescue helicopter, saved the lives of surfer Sam Morgan and bodyboarder Matt Lee, both bitten at Ballina's Lighthouse Beach.

GEOFF THOMPSON: They survived, but it wasn't a guaranteed thing, was it?

GARRY MEREDITH, SURF LIFE SAVING FAR NORTH COAST: No, no. Matt, Matt was very lucky. Like, I don't know if you heard but the, the h, the rescue helicopters: first week they, they were, they were carrying blood. If they weren't-

GEOFF THOMPSON: It was the first week they were carrying blood?

GARRY MEREDITH: Exactly. If they weren't carrying, um, blood supplies, like, I'd hate to think what the outcome would've been.

GEOFF THOMPSON: Garry Meredith has been the first responder at every recent shark attack in Ballina. That experience has diminished his and fellow lifesaver Mark Puglisi's life-long love of the sea.

MARK PUGLISI, SURF LIFE SAVING FAR NORTH COAST: I've had a very, very long history with the ocean. I was a commercial fisherman for many years before I joined the police force.

Um, I've seen a lot of sharks in my time but I don't think I've e-ever seen anything like this. I... I wouldn't say there's any more sharks than what there is, has been for years, but there is definitely more sharks in on the beaches at the moment, and I-I don't know why. I know there's a lot more bait fish, um, around this time this year and last year.

(Aerial footage of beach. Schools of fish show as large black strips and clumps, around 25-30 metres offshore)

GEOFF THOMPSON: These vast black shapes are schools of fish, known as bait balls - and they were drawn to the beaches of the NSW north coast last year. Chasing them were dolphins and big fish, including sharks.

BARRY BRUCE: There was certainly a lot of stuff happening up in the Ballina area last year with schools of bait fish, with whales, with pods of dolphins, with pelagic fish, with sharks moving in the area.

It was a really interesting biological event and I know, when we spoke to locals up there, they were unanimous in that they hadn't seen that sort of bait fish activity in that area for a very long time - or not at all.

So clearly something was going on up there, but th- that's a natural event and, and that's why the sharks were there: because it was a good place to feed.

GEOFF THOMPSON: Surfers in the water were filmed, seemingly unaware of the great whites beneath them.

GARRY MEREDITH: Definitely the bait balls are probably, ah, playing a part in it. But again, I-I've, I've grown here all my life - grew up at Shelly Beach. You know, I've never seen, um... And I surf morning and night. Um, I've never seen sharks in so close, and especially whites, you know? We've - you never see whites.

You often hear the guys, the divers at Byron Bay saying, "Oh yeah, we saw a white on our dive at Julian Rocks," occasionally. But you know, nothing like what we're seeing now.

GEOFF THOMPSON: Are you swimming, surfing? Are you letting your kids swim or surf?

MARK PUGLISI: No and I, um- look, I enjoy swimming at summertime and I've got a couple of little kids. And I was down at South Ballina recently and I would've quite happily 12 m- or 18 months ago put the kids in the water and swam in the channels and that. But there's, there's no way in the world. No, I wouldn't go in there.

GEOFF THOMPSON: Doesn't feel like a safe family outing?

MARK PUGLISI: Not at all. That's - and it's, it's certainly changed things for me. I won't- I-I wouldn't swim in it. I certainly wouldn't. I wouldn't surf: no way, no.

GEOFF THOMPSON (voiceover): The north wall of Ballina's Lighthouse Beach separates it from where the Richmond River reaches the sea.

It's a well known habitat for bull sharks, one of the three species most dangerous to humans and the only shark that swims between fresh and saltwater.

It was a bull shark which mauled 20-year-old pro surfer Sam Morgan here last November; the same spot where a bull shark killed 16-year-old bodyboarder Peter Edmonds eight years ago.

(Geoff Thompson stands on the shore at Lighthouse Beach)

GEOFF THOMPSON: Surfers are out there now, but there's a lot of birds diving for fish and there's dolphins too. It looks pretty sharky to me.

DAVID WRIGHT, MAYOR, BALLINA SHIRE COUNCIL: I feel I feel anxious every day, you know, especially if it's a beautiful day.

GEOFF THOMPSON: Ballina's mayor, David Wright, regularly comes to the north wall. Bull shark sightings are common.

(Footage of David Wright on bluff, speaking with a fisherman on the rocks below)

DAVID WRIGHT: Did you just see a shark a while ago?

FISHERMAN: Yeah, first cast. Came right up behind the lure.

DAVID WRIGHT: Oh. How big?

FISHERMAN: Not that big: five or six feet. Nice and chunky though.

DAVID WRIGHT: Yeah, bull shark.

FISHERMAN: And just as I was bringing the lure up, it came right up behind it and had a swipe at it, right in front of my feet.

DAVID WRIGHT: These guys are actually s- you know, surfing where two of our attacks have taken place, so yes. But we can't force people to get out of the water. It's, um, ah... it's really up to them.

GEOFF THOMPSON: Some locals want shark netting up here. The Government has ruled it out.

DAVID WRIGHT: Certainly the surfing fraternity at the moment would be quite happy with them but, ah, the majority of people up here, particularly in Byron and, and Lennox and, and through here to Ballina: um, they're very, ah, environment conscious so I don't think they'd - and the State Government's not gonna do it.

VIC PEDDEMORS, SENIOR RESEARCH SCIENTIST, FISHERIES NSW: We are committed to protecting people with minimal impact on the environment.

In the northern NSW region there's a very productive and prolific wildlife situation. And putting nets in there would kill a lot of dolphins and a lot of turtles very quickly. And we don't believe that that's necessary.

(Footage of Surfers Paradise Beach, Queensland. Geoff and Natalie Banks are in a boat out from shore)

GEOFF THOMPSON: It's a cost Queensland has been willing to wear in places like the Gold Coast, where sharks and other marine animals are killed with nets and baited hooks, known as drum lines.

NATALIE BANKS, SEA SHEPHERD AUSTRALIA: So there's about 365 drum lines up and down the coast of Queensland and there's about 30 shark nets, just like this one here.

GEOFF THOMPSON: Sea Shepherd took me out to inspect Australia's most extensive and destructive shark mitigation program.

We're just coming up to another section of the net, where those orange buoys are - but in between there's a huge gap.

These nets and drum lines are effective killers. Most of the 78,000 animals caught in them have died.

(Geoff dons a snorkel and goggles and enters the water by a buoy)

GEOFF THOMPSON: So this one of the drum lines that the sharks are meant to take. If there was a shark on it, it would be pulled down or, or moving around. I'm just going to go down and have a look.

(Geoff descends into the water. A massive hook is chained to the buoy.)

GEOFF THOMPSON: As you could see, the baits been taken: probably not by a shark.

(Footage of dolphins picking at the bait on a drum line hook)

GEOFF THOMPSON: This rare footage reveals dolphins carefully picking a drum line clean. They get away with it this time, but are not always successful.

(Footage of baby dolphin caught on drum line hook. Its mother gently nudges it upward to the surface of the water)

GEOFF THOMPSON: Sea Shepherd filmed a baby dolphin hooked on a Queensland drum line. Needing air like we do, it was kept alive only by its mother repeatedly pushing it to the surface.

NATALIE BANKS: So we're seeing dolphins dying. We're seeing turtles. And also rays are dying. We've seen dugongs die in the shark nets, particularly.

Ah, so there's a huge range. It's not just sharks that are dying in these: this is a marine cull as far as I'm concerned.

GEOFF THOMPSON: Twenty-seven species of shark are targeted in Queensland, although most attacks are by tiger sharks.

Thirteen thousand of them have been killed since 1962. But according to marine scientist Jessica Meeuwig, that does not mean people are safer in the water.

JESSICA MEEUWIG, DIRECTOR, CENTRE FOR MARINE FUTURES, UWA: That assumes that there's a proportional relationship between the abundance of sharks and the number of incidents. And actually, the best predictor of the number of incidents is the number of humans.

So... and we've shown time and time again that even when we reduce those numbers it doesn't affect the incident rate, because it's largely a random process. It's a rare, random event and you're- and when it happens to somebody, they're incredibly unlucky.

But there's... Although you'd like to think that there's a relationship there between more sharks equals more bites, it doesn't, it doesn't work that way.

So if 85 per cent of the areas where you put drum lines never had a fatality before the drum lines came on, certainly the fact that there are none since is, is... is misleading to use that as evidence of their benefits.

Um, if you look carefully at that Queensland data, you can see zero safety benefit of those drum lines.

GEOFF THOMPSON: Just like in NSW, Queensland's nets are far from being barriers that stop sharks visiting beaches.

(Footage of Geoff Thompson a few metres away from a long net)

GEOFF THOMPSON: There's a huge hole in that net and a big gap below it. But just over there people are swimming on the Gold Coast without fear of sharks. It's a fascinating difference between the way they're behaving and the people in Ballina are behaving.

Attack survivors have every reason to fear sharks but have very different views about what should be done.

DAVE PEARSON, BITE CLUB: One guy might hate all the sharks and he's got a good reason and he wants to go and kill 'em all. And that's fine. That's, that's what's getting him through. One guy might turn or... to, um, shark conservation and, and want to join that part.

F-For us as a group, we don't buy into any of that. But what we do as a group is support each other.

GEOFF THOMPSON: After being attacked by a bull shark five years ago, Dave Pearson started a support group for survivors, called Bite Club.

GEOFF THOMPSON: But what it is about a shark attack that actually, ah, creates a common feeling?

DAVE PEARSON: The, the thing that I think dawns on me a lot is: it's the, um... it's the thought of being eaten alive while you're still alive. And, um, and-and that is the thing that, you know, eh, this is primal. Like, this is back to caveman days where...

You know, I-I don't want to overdramatise it but it's- that's what it's like. It's, you've got no control over a wild animal trying to eat you. And that's what it's trying to do.

And, and we all hear the, you know, "It's only coming in for an exploratory bite." But when, when you've been taken underwater and you're fighting for your life against a fish, it's not, it's not an exploratory bite, I can tell you, when they're, when they're shaking you around under the water.

GEOFF THOMPSON: Bruce Lucas and Dale Carr were mauled by great whites. Kevin Young is a member because his son Zac was killed by a tiger shark in 2013.

(To Bruce Lucas) What do you think should be done?

BRUCE LUCAS: Just probably more study and research. And will culling help? Maybe, maybe not. But I don't think it's the right way to go.

Just 'cause something... at, at the end of the day we are in their domain. You know, you just don't go around and kill something just for the sake of it.

(Footage of Geoff and Craig Ison walking on beach at Evans Head)

GEOFF THOMPSON: So, Craig, where did it happen?

CRAIG ISON: Just happened out there, Geoff: just, just up beyond that little wave that just broke.

GEOFF THOMPSON: Paddling out early one morning at Evans Head, 40 kilometres south of Ballina, Craig Ison saw the fin and tail of a three-metre juvenile great white shark.

(Craig recreates attack whilst on the beach. He crouches over his surfboard)

CRAIG ISON: Back here's as far as I can go.

GEOFF THOMPSON: Yep.

CRAIG ISON: And with me hand hanging down here like this, lookin'. And that's when I, that's when I saw the shark up in, about six foot up in the air, doing a U-turn face- like, facin' towards like that, to straighten up and come and get me. So: boom, down from that angle.

GEOFF THOMPSON: So you think the shark went deliberately into the air...

CRAIG ISON: Yeah.

GEOFF THOMPSON: ...and turned and targeted you?

CRAIG ISON: Yeah, because he wouldn't have made it. He wouldn't have caught us if he went under the water. He had to actually launch himself up in the air to have a chance to get to us before...

GEOFF THOMPSON: Because it was too shallow?

CRAIG ISON: Yeah.

GEOFF THOMPSON: He wanted you that bad?

CRAIG ISON: He, he wanted us that bad. Yeah, I've never had anything want to kill me so bad in all my life. (Laughs). Never want to experience that.

(Craig Ison shows the underside of his surfboard. There is a shark bite impression, around 50 cm wide and 50 cm long)

CRAIG ISON: So his bottom jaw is in there and his top teeth are on top of my leg. And, and this rail is right up at the end of his... right, so he can't, he can't handle the pressure to, to close it.

GEOFF THOMPSON: He's trying to bite through it?

CRAIG ISON: He's trying to bite through it but he can't because he hasn't got any power there.

GEOFF THOMPSON: Yeah.

CRAIG ISON: And, and he can't release his bottom jaw because they're stuck in the foam on here. And his top, he's thrashing like this. His head's going like this and his whole tail's going whoosh, whoosh, whoosh, like that.

GEOFF THOMPSON: And this is on- this is not here but on your, on your upper leg?

CRAIG ISON: Yeah, on the upper leg. Yeah.

(Craig reveals large, deep scar from shark bite on his upper leg)

CRAIG ISON: Just take, he could have, he would have taken me leg clean off in one go but, like, so I had a good look at those teeth, mate. They weren't baby teeth.

GEOFF THOMPSON: Yeah.

CRAIG ISON: No, he would have, you know...

GEOFF THOMPSON: Craig's left arm was trapped in the shark's mouth, but the former champion boxer refused to give up without a fight.

CRAIG ISON: And unbelievably, the third hit - one I tried to put me fist right through him - after hitting him that, he stopped shaking: just went dead still, went limp. All of a sudden he starts sliding off me, off me leg, off me board.

And and I... (laughs) and the teeth: he went down like that. He's tried to close his mouth but he couldn't and those teeth, all those teeth were like the gates of hell, I'll tell you, mate. They're unbelievable. I'll never forget that.

GEOFF THOMPSON: Are you going to go out surfing here again?

CRAIG ISON: Not unless they've got barriers or nets there. Nup.

GEOFF THOMPSON: So you're done unless it's protected?

CRAIG ISON: Absolutely.

(Newsreel footage of Coogee Beach, archive)

NARRATOR (newsreel, archive): The well known shark-proof enclosure at Coogee Beach, NSW, is a fine example of the combat waged against the shark menace.

GEOFF THOMPSON: Australia's first attempt at shark-proofing a beach was at Coogee in Sydney in the 1930s, after a spate of shark attacks.

A metal enclosure stretched from one headland to the other.

While it was slowly destroyed by surf and salt, sharks were hunted and killed in the belief that attacks were being prevented.

NARRATOR (newsreel, archive): And the head of a man-eating monster appears above the water line.

We can only guess at the number of fatalities which might have occurred had this man-eater been left at large.

GEOFF THOMPSON: Eighty years later, the theory is the same: that reducing local shark populations reduces the chance of attack.

NARRATOR (newsreel, archive): He'll do no more damage. His cruising days are over.

(Newsreel footage ends)

VIC PEDDEMORS: Well, the shark meshing programme has obviously been a long-term program since 1937. The idea has always been to reduce the chance of sharks setting up territories. And that's really how they have worked.

So if, if there were shark nets off an area that, that did historically have a higher shark population, then obviously that shark population would be reduced.

BARRY BRUCE: Shark nets certainly reduce risk because they catch and kill sharks that- that have the potential to bite people. I guess what w- we don't know - we may never know - is to what extent th- the overall risk has been reduced by losing that shark.

GEOFF THOMPSON: Deakin University marine scientist Laurie Laurenson says his research proves that shark nets on NSW beaches do nothing to prevent attacks.

His new statistical analysis has found no relationship between shark populations in netted areas and the number of shark attacks.

LAURIE LAURENSON, MARINE SCIENTIST, DEAKIN UNI.: What we specifically needed to do was look at whether there was a relationship between the numbers of sharks that are out there and the numbers of attacks. And there is no statistically demonstrable relationship. It's not there.

GEOFF THOMPSON: He's analysed decades of data about shark mitigation programs and human populations in South Africa and NSW.

LAURIE LAURENSON: So we got the population size from each area and we related, over the 50-odd years of data, how that population changed relative to the attacks in that area. And there is a relationship between changing population size and the number of attacks of people: that is clear.

So back to the basics: no relationship between the dens- ah, between the numbers of sharks out there. And there is a relationship between the number of people living on the coastline.

GEOFF THOMPSON: The NSW Government has not statistically proven that shark netting makes people safer, but the State's chief shark scientist is a believer.

(To Vic Peddemors) Can you put your hand on your heart and say that you believe the NSW shark meshing program prevents shark attacks?

VIC PEDDEMORS: Without a question of a doubt, I can definitely put my hand on my heart and say that I believe that shark nets work and I believe that you are a lot safer at a netted beach, not only because of the nets but obviously also because they are at patrolled beaches.

LAURIE LAURENSON: I can show statistically that there is no relationship between the number of sharks out there and the number of shark attacks. It's just simply not there. I'm surprised that it's not there, but it's not there.

(Footage of anti-culling protest on Cottesloe Beach, Perth, Feb. 2014)

JEFF HANSEN, SEA SHEPHERD (Feb. 2014): We were never under the illusion that this campaign was going to be easy. We are up against a very powerful Government.

GEOFF THOMPSON: When Western Australia started killing sharks to prevent shark attacks, protesters came out in their thousands.

JEFF HANSEN (Feb. 2014): We have no choice. We have no choice but to take on the Barnett Government.

GEOFF THOMPSON: The protests were triggered by a culling program that started after seven people were killed by great white sharks in just three years.

RYAN SOULIS, SURFER: I noticed its... how round it was. You know, it was really, really big. It was a big fat sort of shark and really beat up, old sort of looking, you know.

And then it went round the back and then surfaced right here and its gills were, gills were probably actually closer than where you are.

GEOFF THOMPSON: Surfer Ryan Soulis supports culling great whites in WA. He watched his best friend, Ben Linden, be taken by one after the shark suddenly lost interest in him.

RYAN SOULIS: Without a doubt in my mind it wanted to eat me, you know. It wanted to eat me. Um, and, that's you, know that's one thing that sort of kills you, but that's one thing that you lose sleep over: definitely that.

Not only did, did it want to eat me, you know, like you had a shark circling, wanting to eat me; but then I saw what it wanted to, to... how it wanted to eat me, you know what I mean? I saw what it did, um, like to my, to my best mate, you know. I mean, that's, that's just terrible.

SHARON BURDEN: It is an incredibly, ah, difficult situation for any community when you are having a, a cluster, which is essentially what happened the year Kyle died.

GEOFF THOMPSON: Sharon Burden's son Kyle was killed by a great white shark while bodyboarding at Margaret River in Western Australia in 2011.

SHARON BURDEN: He was the first of five that died within a short period of time and it is to be expected that people will be very polarised in their views about how and what should be done.

GEOFF THOMPSON: Baited drum lines were set off Western Australia's coast over the summer of 2014.

SPOKESMAN, WA DEPARTMENT OF FISHERIES (archive): Generally they'll be killed with a firearm. That's the most humane method.

GEOFF THOMPSON: They caught 172 sharks in a three-month trial, 163 of them tiger sharks.

Tiger sharks aren't known to have killed anyone in Western Australia for more than 20 years.

Not a single great white was caught.

SHARON BURDEN: My son died from a great white. We don't know which great white shark it was. That great white shark could be anywhere around the oceans in its migratory path at any time. So what is the point of just dragging creatures out of, of the ocean a-and killing them? For what purpose?

GEOFF THOMPSON (To Rick Fletcher): Do you accept that it was a failure? Do you wish it didn't happen?

RICK FLETCHER, DIRECTOR-RESEARCH, FISHERIES WA: Oh it's... I don't see it was a failure: it was a trial. Um, so we, we caught what was... we caught w-what was caught and the Government made a decision based after, after that- the trial ended.

GEOFF THOMPSON: An environmental impact review recommended Western Australia's drum line experiment end.

GEOFF THOMPSON: Do you think the drum line program in Western Australia made swimmers safer and surfers safer?

RICK FLETCHER: Well, that's something that, ah, you prob- could probably only tell if it actually c-continued on. I mean it was a short, it was a short trial program. Ah, the important thing is that during the drum line program no-one was attacked so from that perspective you could actually say it was successful. Um, it certainly wasn't not successful.

(Footage of Geoff Thompson inside surf lifesaver helicopter. The pilot boards and takes off)

GEOFF THOMPSON: There's been one shark attack death in Western Australia since the cull finished.

The state still has a reputation as a place where great whites haunt the beaches.

I went up for a look with WA's Surf Lifesavers.

GEOFF THOMPSON: So if there was a shark here now, you would see it?

BRENDAN CLEAVER: Yep. They-they stand out pretty well on that white sand.

CAMERON COULSON: Ah, different times of the year, obviously the whales are migrating up north. There's increased whale activity and also, yeah, increased shark activity, um, yeah, with the sharks following the whales up and down.

GEOFF THOMPSON: And do you get a lot shark activity around Rottnest Island?

BRENDAN CLEAVER: We tend to, yeah.

GEOFF THOMPSON: There was plenty of life to see from the air: dolphins and fat seals were here in abundance. There were schools of baitfish too. But no sharks.

There's seals lying on the beach, just down here. There's lots of reasons why sharks would like these waters.

But we've just spent almost an hour flying up and down some of Western Australia's most popular beaches, out to Rottnest Island and back. And we haven't seen a single shark.

(Footage of Coogee Beach shark barrier, Perth)

GEOFF THOMPSON: No-one's worried about shark attacks at Perth's Coogee Beach. It's where Western Australia leads the country in effective shark protection.

It's not a net that catches things, but a secure plastic barrier that keeps sharks out.

If you're worried about sharks, this is a secure enclosure. It goes all the way to the bottom and all the way to the top. It's a great net for this beach, where there's calm waters and no serious disturbance. But putting this on a serious surf beach is another question altogether.

A much bigger version will be trialled within the next few months at Ballina's Lighthouse Beach.

DAVID WRIGHT: That'll go from the end of the north wall, right across there to Lighthouse Point. And that means that these surfers will be covered. Um, they'll be protected. Ah, nippers will be OK on the beach and, and plus the, the safe areas for the, ah, lifesavers to, um, patrol and people can swim.

The marine rescue, ah, tower has...

GEOFF THOMPSON: Ballina's shark barrier will have to withstand four-metre swells and driftwood the size of trees.

(Craig Moss demonstrates assembling plastic shark barrier)

CRAIG MOSS, INVENTOR, ECO SHARK BARRIER: The same material as cable ties and fishing lines...

GEOFF THOMPSON: Even the man who makes them isn't certain it will work.

CRAIG MOSS: Yeah, they click together. Put these in...

Yes, it is uncertain. I-it is an untested product on a surf beach. You know, I mean, it's like everything: you have to put it out there to be able to be tested.

I mean, at the end of the day I have seen surf here up to two metres, a metre and a half and it handled it c- ah, well. So I mean, to put it into a surf beach as such at Ballina: for sure it's going to be a test. There's no question.

But, you know, I've put my house on the line for it and I believe that it'll do everything it's supposed to do.

(Footage of Darren Rogers and Geoff Thompson on Shelly Beach, Ballina. They walk out to the water's edge)

DARREN ROGERS: There's a nice little wave there now: ah, that one.

GEOFF THOMPSON: Darren Rogers used to surf every day.

DARREN ROGERS: I believe we possibly have a jet ski out there patrolling for us as well.

GEOFF THOMPSON: Today he's going for a surf for just the fifth time since Tadashi Nakahara was killed.

DARREN ROGERS: It's a good feeling. It's always a good feeling to go surfing.

GEOFF THOMPSON: Oh, yeah.

DARREN ROGERS: Although it has been hard. So...

GEOFF THOMPSON: Diff- been a different feeling lately?

DARREN ROGERS: It's been a very different feeling lately. Yes. Yes, it has.

GEOFF THOMPSON: Darren has a Shark Shield on the end of his board: an electric repellent which has been shown to reduce the chance of attack.

DARREN ROGERS: I'm excited.

GEOFF THOMPSON: I'm a bit nervous.

DARREN ROGERS: I'm a little bit nervous myself. I've been very nervous when I've been surfing alone lately. I'll, um, get the device, which will be hanging from the back of my board.

So we're good to go. So let's, um, go for a surf.

GEOFF THOMPSON: Yeah.

(They enter the water, swim out and have a surf)

GEOFF THOMPSON: We are barely back on the beach before a shark surveillance helicopter is circling, warning people out of the water.

DARREN ROGERS: There's definitely a shark there. This is, ah, the protocol that they do. The shark's just here.

They think that that is a long distance from there and for a shark that's about two minutes. (Gestures to swimmers) So come in. Come on, come in. So, so it's all happening right now. This is the real deal.

GEOFF THOMPSON: A surf school group comes in, but some surfers stay out.

DARREN ROGERS: There's definitely a shark happening right here now. I cannot understand why these two kids aren't coming in.

GEOFF THOMPSON: Darren's memories of what a shark can do come flooding back.

DARREN ROGERS: I'm shaking. My hands are shaking.

I've been through this before and I know what can happen to those two guys. And my whole body's shaking and I'm, ah... and I'm very freaked out right now. It's just a very intense experience overall.

GEOFF THOMPSON: You know, I guess what I can't shake is: we're looking for sharks now. Maybe they're out there all the time. Maybe now we're just hyper-vigilant.

Ah, you know, if you're surfing in... up and down the coast and you're out on a lonely point, you wouldn't know there was a shark there. You wouldn't have the chopper, so you wouldn't get freaked out.

It's hard to know how much fear is tangible and justified and how much is being generated just within us.

Shark attacks are horrifying and the sharks we kill cannot hurt us. The nets and drum lines on our beaches certainly make us feel safer.

But we may have to accept that swimming and surfing in the open ocean is a bit like jogging through a wildlife park.

GEOFF THOMPSON: Did Kyle's death change your relationship with the ocean at all?

SHARON BURDEN: No. I've always loved the ocean. I swim where Kyle was killed, so no. I don't have any, um, concerns.

GEOFF THOMPSON: Yeah. And there's been no incident where Kyle died since?

SHARON BURDEN: No.

If you think about a day like today, all around Australia there would be tens of thousands of people in the ocean today.

We cannot- the government cannot put into place the strategies that will help protect every single one of those people on every single beach around our massive coastline.

There has to be some form of strategy between "don't do anything" and "kill everything".

And there is this area in the middle where we really need people to move to and that is: if I am going to a beach, I need to understand that there is a risk involved in these wild environments.

But what can I do as a parent or as an individual if I'm swimming or surfing or diving that might help reduce those risks?

SARAH FERGUSON: It'll never be completely safe to go back in the water. But what we need is knowledge, based on the best scientific research, to drive that decision - not fear.

Next week, reporter Caro Meldrum-Hanna goes undercover into the wild and often dangerous world of the dance party drug scene.

Australians are the highest recreational drug users per capita in the world. And don't be fooled by the feel-good nickname "party drugs", because they can be deadly.

So what can we do to protect young people from dying to dance?

Until then, good night.