SharkSafe Barrier could protect local swimmers

Magnetic, kelp-mimicking screen from South Africa has UMass Dartmouth connection.

The shark safe barrier mimics kelp, a natural deterrent for sharks. — Courtesy Dr. Sara Andreotti/

The increasing presence of great white sharks in Massachusetts waters had many people thinking twice before taking a dip this past season, especially after the tragic death of 26-year-old Arthur Medici in Wellfleet. The gray seals that white sharks prey on are not only multiplying, but expanding their territories, with colonies now reported on Nomans Land off Aquinnah, and Gull Island amid the Elizabeth Islands. Between the Cape, which teams with thousands of seals, Nomans Land, and Gull Island, the Vineyard finds itself within a triangle of shark food. How Vineyarders can keep these enormous fish at bay — keep them from straying close to beaches and potentially mistaking the outline of a swimmer for that of a seal — is a question gaining increasing currency. A South African startup may have the answer with an screen system called SharkSafe Barrier.

The barrier is a submarine wall of tubes meant to look like a kelp forest. The researchers who developed the barrier calculate sharks are loath to enter kelp forests.

“Sharks need to constantly swim to oxygenate their gills,” marine biologist Sara Andreotti, SharkSafe Barrier’s general manager, said, “so they are likely to avoid an environment that can trap them, obstruct their gills, or simply constrain their movements, such as a thick kelp forest.”

The strands of artificial kelp are also laced with barium ferrite magnets. The magnets irritate electroreceptive pores in shark’s snouts. Sharks use the pores to sense electricity and magnetism. The magnets don’t hurt the sharks, Andreotti said, but they overwhelm the electroreceptive pores, acting as a further deterrent. The magnets do not require shore power, and are encased in a ceramic shell and don’t therefore corrode, she said.

“Michael Rutzen [South African cage diver] had the idea of building an artificial kelp forest as a shark deterrent, to substitute for shark nets, for several years, following his firsthand experiences in diving with the white sharks in open waters,” Andreotti said. Rutzen’s goal was to stop shark deaths from traditional net barriers and drum lines.
Rutzen and Andreotti later met Craig O’Connell, a former Ph.D. candidate at the University of Massachusetts, Dartmouth, who was developing barium ferrite magnets for use in trawler nets to help avoid shark bycatches. The three then translated the magnet idea to the faux-kelp barrier. Andreotti personally tested the barrier by free-diving into chummed waters.
“After the sharks arrived, I had to jump inside the barrier,” she said. “I would say I have a lot of faith in this system.” The white sharks did not attempt to breach the barrier, she said.
Andreotti said she did not believe a white shark chasing a seal would enter the faux-kelp barrier. “If a shark is chasing a seal, it is unlikely that the shark can still swim through four rows of SharkSafe Barrier,” she said. Four rows is the recommended beach design for human safety, she said. Seals pass through it harmlessly, she added. “We are at the stage where we can install the barrier in areas with rocks or less than one meter of sand.”

The kelp barrier “must be about one meter above the water at high tide,” she said. The plastic composing the barrier can be made from 100 percent recycled material.
The barrier runs about $35 per square meter, “calculated on 20 hectares of surfable water,” she said.

The strands of faux-kelp are manufactured in South Africa, while the concrete anchors are molded onsite by a local subcontractor.


  1. Give me an effing break. More people have been killed on mopeds here than sharks but they are still fooling around our roads. Zero shark deaths but we are going to think about installing this? We have become a hysterical society.

      • Yet we still drive cars, mopeds etc. and that happens here!
        It also helps not to look like a seal while swimming with seals.

        • @Salt: Is it time wasted to recommend you read up on the increased white shark population off the Cape and Islands? Surprise us all.

          • Ii’m Very aware. Have Sharktivity installed on my phone. I have gone to talked by Greg Skomal. I had the pleasure of seeing several white sharks cruise the beach near Provincetown while the seals hung out on the shore. They are there all the time yet very few are bitten. I say bitten rather than attacked because that’s what white sharks do. They see something they are curious about that might be a seal and they taste it.
            The man who died as a result of his injuries from being bitten and the man who was badly injured earlier this summer are important and we should care about them. I still see no reason as of yet to put up a shark barrier here.

  2. we cannot protect all people from all possibility of injury or death. There are risks associated with everything.
    Don’t text while driving..

    • It’s been said most shark attacks occur in 4 to 5 feet of water. Why? Because that’s where the people are. Close the beaches? Starting to sound like Mr Benchley’s “Jaws” except this will be real tourist dollars, not movie admission.

  3. Everyone seems so cynical who is leaving a post. This just seems like a creative idea to make people feel relaxed when they swim we shouldn’t be so critical especially since somebody was just killed by a shark this season! Careful not to use the newspaper as a place to vent one’s displeasure as a grumpy old man. Best to be part of a solution in a positive way than to criticize those that are trying to do good.

  4. I like Mike’s idea about sealskin clothing. Imagine boot tops that don’t ice up so easily when tromping through wet snow!

    Total protection of an animal leads to over population problems down the line. What is the end game plan, wait until the fish population plummets and there is a big seal die off? And if there were a seal die off, what would the sharks turn to for food? A regulated harvest of the seals to keep their population at a sustainable level would be more balanced, even if less emotionally appealing. If the skins and/or meat had some value the harvest would pay for itself, no need for further tax dollars to cover the barrier. Think of the amount of beach frontage that would need to have the four barriers! Think of deliberately adding all that plastic to the ocean! Being near the shore would also mean storm damage and loose plastic floating around. Are the plastic tubes able to wrap a propeller? Further, modern rare earth magnets should be saved for useful generation of electric power in turbines and vehicle braking, not used to help pollute the ocean. And imagine trying to use a magnetic compass on your boat near a shore with a barrier loaded with magnets. Or floating tubes that broke free and are near enough or even entangled in your vessel deflecting your compass.

    Personally, I did not find the single “test” of the barrier to be convincing. After all the claims we have heard that sharks don’t like people why should the shark follow a person though the barrier? Perhaps chum inside the barrier, or have a seal inside the barrier. Certainly a genuine test would be in order.

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