There are a range of shark attack prevention techniques employed to reduce the risk of shark attack and keep people safe. They include removing sharks by various fishing methods, separating people and sharks, as well as observation, education and various technology-based solutions.

Techniques that involve culling sharks are contentious. Environmental groups have voiced concern over the impact of reduced shark numbers on ocean ecosystems and the problem of by-catch of other marine life, particularly endangered species.

The majority of shark nets used are gillnets, which is a wall of netting that hangs in the water and captures the targeted sharks by entanglement.^[1] The nets may be as much as 186 metres (610 ft) long, set at a depth of 6 metres (20 ft), have a mesh size of 500 millimetres (20 in) and are designed to catch sharks longer than 2 metres (6.6 ft) in length.^[2]

Shark nets do not offer complete protection but work on the principle of "fewer sharks, fewer attacks". They reduce occurrence via shark mortality. Historical shark attack figures suggest that the use of shark nets does markedly reduce the incidence of shark attack when implemented on a regular and consistent basis.^[3][4][5]

A downside with shark nets is that they do result in bycatch, including threatened and endangered species.^[6]

Total cost for the shark netting program in New South Wales for the 2009/10 year was approximately A$1 million, which included the cost of the nets, contractors, observers and shark technicians, shark meshing equipment (dolphin pingers and whale alarms etc.), and compliance audit activities.^[7] For the 51 beaches protected,^[7] this represents a financial cost of approximately A$20,000 per beach per year.

A shark barrier (otherwise known as a "shark-proof enclosure" or "beach enclosure") is seabed-to-surface protective barrier that is placed around a beach to separate people from sharks. Shark barriers form a fully enclosed swimming area that prevents sharks from entering.^[8] Shark barrier design has evolved from rudimentary fencing materials to netted structures held in place with buoys and anchors. Recent designs have used plastics to increase strength and versatility.

When deployed in sheltered areas shark barriers offer complete protection and are seen as a more environmentally friendly option as they largely avoid bycatch. However barriers are not effective on surf beaches because they usually disintegrate in the swell and so are normally constructed only around sheltered areas such as harbour beaches.^[9]

A shark barrier installed at Middleton beach in Albany, Western Australia cost A$340,000 to install, with annual maintenance budgeted at A$30,000 per annum.^[10] On Réunion Island in 2015 two shark proof enclosures cost €2 million to install and €1 million a year to maintain.^[11]

A drum line is an unmanned aquatic trap used to lure and capture large sharks using baited hooks. They are typically deployed near popular swimming beaches with the intention of reducing the number of sharks in the vicinity and therefore the probability of shark attack. Drum lines were first deployed to protect users of the marine environment from sharks in Queensland, Australia in 1962. During this time, they were just as successful in reducing the frequency of shark attacks as the shark nets.^[12][4][5] More recently, drumlines have also been used with great success in Recife, Brazil where the number of attacks has been shown to have reduced by 97% when the drumlines are deployed.^[13] While shark nets and drum lines share the same purpose, drum lines are more effective at targeting the three sharks that are considered most dangerous to swimmers: the bull shark, tiger shark and great white shark.^[14]

In 2014 a three-month trial utilising up to 60 drum lines in Western Australia cost A$1.28 million.^[15]

Drum lines have been criticized for being environmentally destructive and speciesist, and have sparked public demonstrations and vocal opposition, particularly from environmentalists, animal welfare advocates and ocean activists.^{[16][17][18][19]}

Shark-spotting programs using drones, fixed wing aircraft, helicopters, Beach patrols, observation towers and even blimps, are being used and trialled in various locations across the globe.^[20] However visability issues with water clarity can be a problem particularly with aerial patrols, which have been found to identify less than 20% of sharks present.^[7][21] There is also the financial cost of hiring aircraft and/or personnel to conduct the surveillance.^[20]

Across the world a sample of sharks have been tagged with electronic devices that transmitt their location^[22]. Acoustic tags transmit pulses which are detected by underwater listening stations when the sharks swim close by, typically within 500 metres.^[23][20] Fin-mounted satellite tags are also commonly used.^[20] These tags allow shark movements and behaviour to be monitored and studied and swimmers and surfers can be warned if a shark is detected close to shore.^[23]

However a limitation with the system is the tagging will only highlight a very small portion of the dangerous sharks present.^[20] It also may lead people into a false sense of security.^[20]

Shark Shield is a personal electronic device that creates an electromagnetic field to deter shark attacks and is used by surfers, scuba divers, spearfishing, and ocean kayak fishing. It is the only electrical device on the market that's been independently verified to be effective at deterring shark attacks.^[24] However note that the Shark Shield does not work in all situations^[25][26][27] and divers have been attacked whilst wearing Shark Shield.^[24][28]

The West Australian government has also announced that they are supporting the Shark Shield FREEDOM 7 via a A$200 subsidiary.^[29] However as at April 2017 only the diver version of Shark Shield has been approved for the rebate.^[29]

A shark repellent is any method of driving sharks away from an area and includes magnetic shark repellent, electropositive shark repellents, electrical repellents (including Shark Shield) and semiochemicals. One example is a product called Anti-Shark 100^[30] which is an aerosol can that contains an extract of dead shark tissue. There is a range of evidence that supports the effectiveness of this product,^[31]

Other examples of personal shark protection technologies include wearing interruption patterned or camouflage wetsuits, ^[32] magnetic repellents incorporating a small magnet in a band worn on the wrist or ankle,^[31] acoustic repellents that mimic the sound of orcas^[24] and changing surf board colours.^[20]. However none of the products associated with these technolgies have been independently tested.^[24][20][31]

There are documented instances of bottlenose dolphins protecting humans from shark attacks, one off the coast of New Zealand in 2004^[33] and one attack on a surfer in northern California in August 2007.^[34] There is no accepted explanation for this behavior; as mentioned in the Journal of Zoology, "The importance of interactions between sharks and cetaceans has been a subject of much conjecture, but few studies have addressed these interactions".^[35] In some cases, sharks have been seen attacking, or trying to attack dolphins.^[36] The presence of porpoises does not indicate the absence of sharks as both eat the same food.^[37]

In Queensland and NSW systematic long term shark control programs using shark nets and drumlines are utilised to reduce the risk of shark attack. Since 1936 sharks nets have been utilised off Sydney beaches.^[38] Nowadays they are employed on both NSW and Queensland beaches; 83 beaches are meshed in Queensland compared with NSW's current 51.^[38][39]

The technique of setting drum lines is also used in Queensland and New South Wales, where they have been used in association with shark nets. Before 1962, there were 82 recorded attacks. Since the policy was implemented there has only been one recorded death, at Amity Point in January 2006. 21-year-old Sarah Kate Whiley was attacked by as many as three sharks in Rainbow Channel. The attack occurred in an unpatrolled area.^[40] Queensland Fisheries Minister John McVeigh has described the longevity of the netting and drum line program as being "a good indicator that it had the support of most Queenslanders".^[41]

The baited drum lines attract sharks from within a 3–5 km radius, preventing sharks from reaching swimming areas. They also capture less bycatch than shark nets.^[14] Darren Kindleysides, director of the Australian Marine Conservation Society, has acknowledged that nets in Queensland have worked, "but at huge cost to whales, dolphins and turtles".^[42]

There were a total of 97 fatalities attributed to shark attacks in Queensland between 1858 and 2014. In New South Wales there were a total of 96 fatalities attributed to shark attack between 1771 and 2014.

The Western Australia government deploys drum lines under certain circumstances under its "imminent threat" policy. They can be deployed in the event of the appearance of a shark or sharks that present a possible threat to public safety.^[43] This follows the abandonment of seasonal drum line deployment plans in September 2014, after the state's Environmental Protection Authority advised against extending the Government's catch and kill shark policy.^[44]

Western Australia also deploys shark enclosures in a range of locations^[45] as well as aerial shark spotters, beach patrols, shark tagging efforts and associated tracking and notification systems.

There were a total of 111 unprovoked shark attacks in West Australia between 1870 and 2016, including 10 fatalities since 2010.^[46]

In South Australia, spotter planes and a small number of patrolled swimming beaches are the only methods used to mitigate the risk of shark attack. On 6 February 2014, Port Lincoln tuna "baron" Hagen Stehr expressed his support for the Western Australian shark cull. He also stated that his business' spotter planes had observed increases in great white shark numbers off the west coast of Eyre Peninsula. He acknowledged that his tuna farming operations attract some sharks. He told The Advertiser that he believed "selected culling of sharks is a must. It is crazy stuff to put them under protection so it becomes a major offence to kill them."^[47] Critics of Stehr's stance note that a cull of sharks in SA would be beneficial to his business, as tuna is a major source of food for sharks. Shark attack survivor turned conservationist Rodney Fox has spoken out against the cull, saying "When a shark attacks someone, we go 'the shark needs to be punished'. They don't live under our laws. It's a different world down there and it should be treated differently."^[48]

At September 2014, there had been a total of 82 shark attacks in South Australia since 1836, including 20 fatalities.^[49]

In KwaZulu-Natal, South Africa a long term shark control program utilising a combination of shark nets and drum lines are used to mitigate the risk of shark attack. The region's shark attack statistics primarily reflect the effectiveness of netting, as drum lines were only introduced recently, following their successful use for over 40 years in Queensland, Australia. The Board states "Both types of equipment function by reducing shark numbers in the vicinity of protected beaches, thereby lowering the probability of encounters between sharks and people at those beaches." At Durban, from 1943 until the installation of shark nets in 1952, there were seven fatal attacks. No fatalities at Durban and no incidents resulting in serious injury have occurred since nets were installed there. At other protected beaches in KwaZulu-Natal, from 1940 until most of those beaches were first netted in the 1960s, there were 16 fatal attacks and 11 resulting in serious injury. In the three decades since nets were installed, there have been no fatal attacks at those beaches and only four resulting in serious injury.^[50] It is unclear whether more sharks caught on drum lines survive when compared to shark net captures in KwaZulu-Natal, but the lines have shown reduced non-target species bycatch. Drum lines set in the region are baited with 500 grams of meat per hook and are believed to only attract sharks from several hundred metres away.^[51]

Seasonal and temporary bathing bans and "discretionary bathing" are additional strategies employed in the region. Bans often follow net displacement or damage due to storms or swell, or net removal due to whale stranding. Nets are also removed during the annual sardine run to limit the degree of bycatch during the event. Pressure from the tourism industry to reinstate nets during the sardine run has previously proven "disastrous", resulting in large numbers of shark and dolphin mortalities.^[50]

In Hawaii, seven short term shark culls utilising long-lines took place between 1959 and 1976.^[4] During this time, 4,668 sharks were caught, at a cost of US $300,000. Although the Hawaiian resident and tourist human population increased dramatically, the number of shark attacks remained constant (in contrast to Florida, where the number of shark attacks has increased in line with human population increases) and the short term programs were not considered a success by the authors of a shark culling study.^[4][52] The study concluded that the culls "do not appear to have had measurable effects on the rate of shark attacks in Hawaiian waters".

The publication came at a time during intense community debate over culling in Hawaii, documented by local journalist Jim Borg in his 1993 book, Tigers of the Sea, Hawaii’s Deadly Tiger Sharks.^[53] Borg detailed the debates between the study’s authors and other scientists who argued that the experiences of South Africa’s KwaZulu-Natal Shark Board^[54] demonstrated the effectiveness of the culling. The debate began with the November 1991 shark attack killing of Martha Morrell off Maui and embroiled the subsequently formed Hawaii Shark Task Force, Borg writes.

Statistics from 2013 showed the number of shark attacks in Hawaii was spiking.^[55]

Drumlines and long lines have been used successfully in Recife in a long term program, where shark attacks have been reduced by around 97%.^[13] Sharks are initially caught on baited drum lines (similar to those in Western Australia). Once captured, the sharks (if found alive) are humanely handled and tagged.^[56] They are then relocated offshore and their movements are tracked. The project is known as the Shark Monitoring Program of Recife (SMPR). A report assessing the program's performance was published in 2013. It stated: "Overall, the SMPR seems to be less detrimental than shark meshing strategies while clearly contributing for enhancing bather safety; thus, it may provide an effective, ecologically balanced tool for assisting in shark attack mitigation."^[13]

The prevalence of shark attacks at Réunion Island—there were 19 attacks between 2011 and 2016, including seven which were fatal—prompted Réunion island's government to carry out a range of systematic long term shark protection activities, including a shark cull, utilising "smart" drumlines and longlines.^[57][58] In the five years to August 2016, more than 170 sharks were killed as part of the cull.^[59]

In 2015, two shark-proof fences were strung at beaches to the west of the island, at a cost of €2 million. Maintenance of the fences is projected to cost €1 million a year.^[11] The protective nets / shark enclosures at the two beaches have a total length of just under 1 mile and are subject to damage from heavy swell. On 27 August 2016 a surfer lost an arm and a foot from a shark attack while surfing within one of the enclosures. It was reported that at the time of the attack there was a two-meter hole in the nets, most probably caused by the swell.^[60]