By Mark Robinson

“There are angel sharks, goblin sharks, crocodile sharks, bramble sharks, monk sharks, carpet sharks, swell sharks, nurse sharks, silky sharks, cow sharks, bull sharks, basking sharks, frilled sharks, cat sharks, leopard sharks, dogfish, hammerheads, porbeagles, and wobbegongs, but the species that comes to mind when we think of attacks on us is the great white shark, Carcharodon carcharias.”
From Great White Sharks
by Richard Ellis and John E McCosker

We'd just up-anchored when the white pointer barrelled in toward the stern of the boat, a brown-grey missile moving with deceptive speed. At the last second it rolled its nictitating membrane shut to protect its eyes, but not before we had looked into the depths of those alien black holes.

Its huge jaws opened wide and then clamped down; not on a juicy bait but on a spinning propeller. The 150hp outboard stalled immediately. The pointer shook its body from side to side, causing the whole craft to shudder violently and making those of us aboard wonder if the transom was going to be ripped out and we’d be next to disappear down its huge maw.

“In a heart-stopping moment, it reared up its huge head to be almost level with us, its black eyes boring into ours…”

Garry began to bash it on the side of its head with a two-metre long gaff handle, while Fitzy started throwing chunks of bluefin tuna overboard in an attempt to distract it. The blows Garry was landing didn’t seem to be fazing it in the slightest and I was about to load the power-head that we carried aboard when the big fish lost interest in the prop. Then, in a heart-stopping moment it reared up its huge head to be almost level with us, its black eyes boring into ours, before disappearing back into the depths.

The foregoing is a true account of an incident that occurred some years back when it was legal to fish for sharks. As a long-time member of the Game Fishing Club of South Australia, I’d done my fair share and more, winning a number of club trophies by specialising in fishing for these toothy critters. But the more I fished for sharks and the more encounters I had with them, the more it made me reflect upon my years of surfing and my three decades of spear fishing and scuba diving.

Over the years I’d read of many experiments on shark repellents like the attempts made during World War II when the US Navy created ‘Shark Chaser’, a mixture of copper acetate and black dye made to smell like a rotting shark. Needless to say, scientists later determined it was ineffective. More recently, a New Jersey company has developed a chemical repellent based on substances found in dead sharks. So far they reckon that it has worked on four species, none of which is particularly threatening to humans; the Caribbean reef shark, the blacknose shark, the lemon shark and the nurse shark.


The Mariner unit creates a ‘safety zone’ around the rear of a vessel when used as above

As someone who has successfully caught sharks using bits of dead shark for bait, I don’t have high hopes for their efforts, especially considering the earlier lack of results when a University of Maryland professor found that a fish swimming in the Red Sea, known as the Moses sole, secreted a natural shark repellent. Researchers from the University of Miami and a team of Israeli and Egyptian scientists worked on replicating the milky liquid, but gave up once they realised it worked only when injected directly into a shark’s mouth!

Based on the relevant literature available to hand, it seems unlikely that the future lies in any sort of chemical repellent. In this age of high-technology, it would seem the answer lies in the electronic arena. A hungry shark might not like a particular smell, but experience suggests that it is still likely to swim up and taste it anyway. And the way sharks like to taste things is to take big bites out of them…

Aussie company, SeaChange Technology, reckons it has found the answer with a device called Shark Shield, which generates a unique electronic wave-form, said to deter sharks. Its history is quite interesting and its pedigree impressive.

South Africa, like Australia, is a known haunt for great whites and holds the unenviable record of some 204 documented shark attacks, of which 41 were fatal. Of these attacks, a whopping 91 (27 of these were fatalities) took place in the waters off the province of KwaZulu-Natal, previously known as Natal. So there was more than a little motivation for the local authorities to improve the situation, especially given the role tourism plays in their economy.

South Africa’s most populous province, Natal possesses a magnificent stretch of coastline featuring an endless succession of broad, unpolluted beaches and crystal-clear lagoons, with rocky outcrops washed by the warm Indian Ocean. It offers wonderful swimming, great surfing and world-class scuba diving. It is also home to way too many sharks; at least in the minds of many potential tourists.

In the early 1990s, scientists from the Natal Sharks Board of South Africa discovered an electronic wave-form, which deterred sharks and had the huge advantage of not adversely affecting any other form of marine life. After many years of research, this technology was developed and incorporated into a product known as the Shark POD.

Early successful testing using electrical discharges (above).


As the recent spate of fatal and non-fatal attacks have emphasised, we sun-bronzed Anzacs appear to have a growing problem with more sharks coming in closer to shore and attacking divers, swimmers and surfers. In fact, Australia ranks second behind the United States on arguably the world’s least enviable league tally– shark attacks. During 2004, the US topped the table with 30, while Australia had 12, according to the International Shark Attack File at the Florida Museum of Natural History.

If 12 attacks sound a lot less than 30; consider for a moment the relative populations of the two countries and it might just hit home how high our risk is compared with theirs. Whether the increasing number of attacks is a symptom of declining fish stocks world-wide or an upward population fluctuation in white shark numbers is moot. Perhaps it is both.

I live close to where Nick Peterson was attacked while riding his surfboard at Adelaide’s West Beach in December last year. Witnesses stated that Nick fell from the surfboard when two great white sharks – both as long as five metres – attacked him only about 300 metres from the crowded beach.

Let me tell you that for several weeks of high summer, day after day, there was the unusual sight of almost-deserted beaches and virtually no one in the water. West Beach is very close to Glenelg, where the Flinders University research scientist, marine biologist Jarrod Stehbens, was recently fatally attacked while diving on the offshore tyre reef. What long term effects these attacks will have on tourism in our region remains to be quantified, but they are certain to have a significant negative impact.


Some years back, the farsighted folks at SeaChange Technology in Adelaide, recognising the huge potential market for devices that would effectively deter sharks from attacking humans, negotiated a worldwide exclusive licensing agreement with the Natal Sharks Board in South Africa. The agreement allows them to utilise the unique patented wave-form electrical discharge developed by the NSB in a range of shark deterrent products, now known as Shark Shield.


The Freedom 4 unit for watersport enthusiasts.

To understand how the Shark Shield works, we need to take a look at a unique characteristic possessed by sharks and a few other fishes. You see, sharks have the same five senses we do – smell, taste, touch, sight, and hearing – but they also have a sixth sense called electroreception, which allows them to detect electrical signals.

These signals are detected by sensory organs called ampullae of Lorenzini, which are located on the head. Ampullae of Lorenzini are deep, jelly-filled pores, connected to nerves. These special organs allow the shark to detect the electrical signals produced by the muscles of their prey. All muscle activation results in electrical activity and the creation of small currents; a phenomenon widely used in medicine, an example of which is an ECG or electrocardiograph which measures and records the electrical activity of the heart muscles.

The ampullae of Lorenzini are extremely sensitive and able to detect electrical discharges as small as .005 microvolts. Now let’s try and put that in perspective. Scientists have estimated that these ampullae collectively give a great white shark the ability to sense the electrical field distributed by a copper wire 1000 miles long hooked up to a D-sized battery!

This is an incredible sensitivity and is due to both the large number of ampullae on each shark and also the fact that each ampulla utilises a large number of sensory cells to detect the signal. These sensory cells lie inside alveoli; small sacs within each ampulla, which are in turn connected directly to the shark’s brain.

It follows logically that if these ampullae are so sensitive to tiny currents, that an electrical field of some strength would be a very nasty experience for the shark that encountered it.


“Logically, an electrical field of some strength would be a very nasty experience for the shark that encountered it.”
The electrical field created which protects a diver.



The Shark Shield generates just such an electrical field, which causes intense muscular spasms in the creature; spasms that result in the shark being deterred from the area. The field is projected from the unit by two electrodes, which create an elliptical field that surrounds the user and both electrodes must be immersed in the water for the process to work.

As one would expect, in order for the Shark Shield to operate effectively, the unit must be switched on when the user enters the water, left on for the duration of the user’s time in the water, then switched off as the user exits the water.

So far, so good. The theory sounds fine and the claimed test results are certainly encouraging. So was watching video footage of both a great white and a mako shark being deterred by the unit. These can also be viewed by logging on to the Shark Shield website at

The effects of the shark encountering the field have been described by divers as like “hitting the wall” and their abrupt change of direction certainly fits that description. Research has shown that while the shark experiences an extremely unpleasant sensation, which makes them veer away and leave the area, there isn’t any permanent harm done to the creature and other forms of marine life are unaffected.

SeaChange Technology describes Shark Shield as an electronic shark deterrent that allows both water sport professionals and recreational users to enjoy their chosen activity with a new dimension – safety and peace of mind – for themselves, their families and employers/supervisors.

Operation of the units could not be simpler as it is simply a matter of attaching the unit to the lower leg using the supplied Velcro strap and then turning it on when entering the water. The units consist of the electronic module and two electrodes in an antenna, which trails unobtrusively behind the user. The units themselves are compact and have an in-water weight of just 200 grams.

Users report no difficulty at all with the trailing antenna, even when diving among staghorn coral, caves and amongst very rocky outcrops. The units are claimed to be extremely reliable, with all electronic components totally encased in resin to prevent water ingress, while the main body of the unit itself is high impact plastic and the battery is the very efficient NiMH type.


Of special interest to boat owners is the Mariner unit, which was originally designed for professional abalone divers, but has found ready acceptance with the recreational boating fraternity. By hanging this unit over the stern, a safe swimming zone is created and it also provides protection for swimmers or divers during water entry and exit.

The popular, lightweight Freedom 2, which creates a ‘deterrent field’ for a snorkeller (right).

SeaChange Technology has a range of products catering for professional and recreational divers, snorkellers, swimmers, surfers, spearfishers, kayakers, boat owners and commercial fishermen, as well as emergency, police and military personnel around the world.

I must admit to being most impressed with the very long list of government, professional and military and rescue organisations using the Shark Shield product, which was supplied to me by SeaChange Technology’s Paul Lunn.

I’ve known Paul since the early days of scuba diving and can vouch for the fact that both his many years of professional diving and managing a dive shop make him uniquely qualified on the risks associated with the underwater environment.

We’ve had a number of lengthy discussions regarding Shark Shield and the media-driven shark phobia; a seemingly unstoppable phenomenon. Well, unstoppable before Shark Shield that is. As Paul says, “Sharks are not a great problem, but they hide in the recesses of our mind and play tricks on our imagination. They detract from the beauty and worry our loved ones”. Shark Shield claims to overcome this and Paul says that time and again people report that they never would have believed that this technology could have added such a new level of enjoyment in their chosen water sport activity.

As a surfer and diver, I tended to think in terms of these two markets when considering the potential of this technology, but as Paul pointed out, many others are out there and to take but one example, the sea kayak and canoe market is just as large as the dive market. When you look into it, the potential is enormous and includes such applications as being used on prawn trawler nets to prevent both loss of catch and damage to nets, plus protection of fish stocks in aquaculture pens.

Regular ocean swimmers can enjoy their swim with complete peace of mind using the Shark Shield Freedom 4 unit, which was originally designed for spear fishing to protect both the spearo and his catch, but which has been enthusiastically adopted by many swimmers and snorkelling enthusiasts.


Paul explained to me that comprehensive testing of these units is carried out in either South Australia or South Africa and then approval for release is granted by the Natal Sharks Board. These tests are carried out on large great whites under the best possible conditions to excite the shark. One novel fact about this technology is that larger sharks have more developed ampullae of Lorenzini and are actually easier to deter than smaller sharks.

In order to excite the sharks, a berley trail is set up along with a hefty tuna bait, and as an experienced shark fisho, I can attest to the fact that this does get these toothy critters very excited. Naturally, these tests are conducted well offshore and away from areas frequented by divers, swimmers, surfers or other recreational water users. Over the years, literally thousands of test replications have been carried out with 100 per cent effectiveness, claims Lund.

During my research into this technology, a sad and sobering part was reading a coroner’s report into the death of scallop diver, 23-year-old Paul Buckland, who died from shark attack injuries off Smoky Bay in South Australia in 2002. Coroners have a great deal of responsibility and they weigh both their words and conclusions very carefully indeed. So I thought it a pretty impressive testament to the Shark Shield technology that the coroner’s report concluded in part that: “I therefore recommend, pursuant to Section 25(2) of the Coroners Act, that commercial and recreational divers, when operating in waters where there is a risk of the presence of sharks, should wear a shark repellent device of the ‘Shark Pod’ or ‘Shark Shield’ type”.

With the ongoing development of this technology by the boffins down at SeaChange Technology, the future looks bright for both humans and a whole range of creatures to enjoy their time in the sea, without fear of being attacked and/or eaten. Currently, products are in the wings to provide a high output shield to replace the beach nets that kill dolphins, whales, turtles and other species. This will truly be a win-win situation for both us and them. And even radical wildlife activists, the kind that would hug sharks if they could (I’d like to see that!), will be happy as no sharks are harmed in the process.

If you dip more than your big toe in the ocean, I’d seriously recommend that you consider one of the protective products from SeaChange Technology. Their Aussie distributor, Australian Ocean Security can be found at