earth science

Ocean Guardian

Ocean Guardian is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Ocean Guardian rather than just read about it. In short: Ocean Guardian was the manufacturer of Shark Shield shark repellent devices. The Ocean Guardian electronic devices create an electromagnetic field to deter shark attacks and are used by surfers, scuba divers, snorkelers, spearfishers, ocean kayak fishers, swimming areas off boats and for ocean fishing.

Key takeaways

Ocean Guardian belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Ocean Guardian to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Ocean Guardian from memory before moving on to harder problems.

Reference excerpt

Ocean Guardian was the manufacturer of Shark Shield shark repellent devices. The Ocean Guardian electronic devices create an electromagnetic field to deter shark attacks and are used by surfers, scuba divers, snorkelers, spearfishers, ocean kayak fishers, swimming areas off boats and for ocean fishing. It is considered one of the few electrical devices on the market that has performed independent trials to determine its effectiveness at deterring shark attacks, Whilst it is noted the Shark Shield technology does not work in all situations, modelling research from Flinders University in 2021 indicated that the proper use of personal electronic deterrents is an effective way to prevent future deaths and injuries, and estimated that these devices could save up to 1,063 Australian lives along the coastline over 50 years. Following Insolvency and Liquidity issues Ocean Guardian collapsed in 2024.

History The original waveform used in the shark repelling technology was devised by three inventors, Graeme Charter, Sherman Ripley, and Norman Starkey, and released in 1995 by POD Holdings Ltd, a joint venture company partly owned by the Natal Sharks Board and the South African government. In the late 1990s the KwaZulu-Natal Sharks Board developed the first electrical shark deterrent, the SharkPOD (protective oceanic device or simply POD). In 2001, the KwaZulu-Natal Sharks Board ceased distribution of the SharkPOD. All rights to the intellectual property were licensed to a South Australian-based company, SeaChange Technology Holdings, which developed various new application patents resulting in a commercial product line under the brand name Shark Shield in April 2002. In 2007, the company introduced the third generation of products to replace the original FREEDOM4 and DIVE01, expanding the range of products offered to include the SCUBA7 (replaced the DIVE01) and introducing two new designs: the FREEDOM7 (replaced the FREEDOM4), a versatile option that can be used by a broad range of ocean-users, including scuba divers, spearfishers, boaters, and kayakers; and the SURF7, designed to be fitted onto a surfboard or stand-up paddleboard to offer surfers protection from sharks. The Shark Shield technology was further developed by the Australian company SeaChange Technology Holdings Pty Ltd, and commercialized by its trading company Shark Shield Pty Ltd established in October 2006. SeaChange Technology Holdings Pty Ltd changed its name to Ocean Guardian Holdings Limited in 2018 with Shark Shield Pty Ltd trading as Ocean Guardian. In 2016, with research and development funding from the Western Australian government, Ocean Guardian announced the FREEDOM+ Surf a product designed in partnership with two times World Champion surfer Tom Carroll specifically designed for surfers. The new design removed the trailing antenna of the older SURF7 being replaced with a sticker-thin antenna on the underside of the surfboard, with the fully transferable power module located in the kicker of the tail pad. In January 2019 the company announced the world's first handheld electrical shark deterrent based on Shark Shield technology called the eSPEAR. The eSPEAR is designed primarily for spearfishermen, divers and snorkelers. The Ocean Guardian product line was further expanded to include the BOAT01 to create a safe swimming area around vessels, and the FISH01 to assist ocean fishermen land their catch without being taken by sharks. On May 26, 2017 the Western Australian government implemented a $200 consumer rebate for scientifically proven electrical shark deterrents. The Ocean Guardian FREEDOM7 and FREEDOM+ Surf are the only products approved. In addition to traditional ocean sports, Ocean Guardian products are in use with various government bodies including police and navies, and were used by production members in the filming of both The Shallows and USS Indianapolis: Men of Courage. Long-distance swimmer, Diana Nyad, in her swim crossing from Cuba to Florida without a cage, used Shark Shield. In May 2024 Ocean Guardian was placed in Administration and in September 2024 the Company was Liquidated.

Functionality All chondrichthyans have highly sensitive electrical receptors called the "ampullae of Lorenzini" located in their snouts. These tiny gel-filled sacs sense electric current from prey at very close distances, typically less than one meter. The jelly is highly conductive and allows the electrical potential at the opening of the pore to be transferred to the ampulla. They use these short-range sensors when feeding or searching for food. They do not use electrical receptors to track animate objects over long distances; other senses such as audition and olfaction are the primary drivers. Ocean Guardian devices create an electrical field that creates an unpleasant sensation impacting the shark's ampullae of Lorenzini. When the shark comes into the range of the field, it experiences uncontrollable muscular spasms, causing it to flee the area. The field is projected from two electrodes, which create an elliptical field that surrounds the user. Both electrodes must be immersed in the water for the field to be created. Research conducted by the South African National Space Agency in 2012 estimated the Shark Shield electrical field to be about 4–5 m in diameter. While sharks are attracted to electromagnetic pulses produced by potential prey animals, the electronic field emitted by the Shark Shield does not attract sharks to the device, so would not increase the risk of attracting sharks to the vicinity of the user. A shark's sensory organs are acutely sensitive to low-voltage gradients (> 5 nVcm), enabling them to detect very low-frequency electronic fields between 1 and 8 Hz at short range, after which the other senses (sight, chemoreception, and mechanoreception) aid the shark in capturing its prey. The range at which an electronic shark deterrent emits a field that is the equivalent of a prey-like stimulus (about 1–100 nV/cm) is much further than their short-range detection facilitates. Should a shark approach the device, the strength of the electric field gets stronger the closer it gets, and soon causes the shark extreme discomfort, forcing it to turn away. Scientific studies modelling this effect show that the output produced at a 3-m distance is far greater than that produced by prey, and drops off significantly beyond a 6-m radius, where it is beyond the short-range detection ability of a shark.

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Ocean Guardian

Start with the simplest possible case. Write down what Ocean Guardian claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Ocean Guardian before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Ocean Guardian ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Ocean Guardian

In research: Ocean Guardian appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Ocean Guardian in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Ocean Guardian is common in secondary-school and first-year university syllabi. It links to neighbouring topics Shark attack prevention, South African inventions, Underwater diving safety equipment, so understanding it makes those chapters shorter.
In everyday life: Look for Ocean Guardian outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Ocean Guardian in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Ocean Guardian means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Ocean Guardian out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Ocean Guardian in simple terms?

Why does Ocean Guardian matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Ocean Guardian?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Ocean Guardian.