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A shark repellent is any method of driving sharks away from an area. Shark repellents are a category of animal repellents. Shark repellent technologies include magnetic shark repellent, electropositive shark repellents, electrical repellents, and semiochemicals.
Shark repellents can be used to protect sharks by driving them away from areas where they are likely to be killed by human beings; in this case, the shark repellent serves as a conservation method.
There is evidence that surfactants such as sodium lauryl sulfate can act as a shark repellent at concentrations on the order of 100 parts per million. However, this does not meet the desired "cloud" deterrence level of 0.1 parts per million.
Research indicates that sharks will avoid an area when they smell chemical released by dead and dying sharks. Six chemicals were synthesized from shark glands and tissues and used in experiments. Sharks immediately reacted once they detected these chemicals. To quote a 2004 Associated Press article, "Fisherman and scientists have long noted sharks stay away if they smell a dead shark."
There have been significant advances in the research, development, and testing of aerosol shark repellents that repel sharks through replicating the chemicals that sharks emit when they die or are in danger. The scientists behind these advances, Dr.Eric Stroud and Dr. Patrick Rice, operate a company dedicated for the research and development of such shark repellents. Their organization, SharkDefense, is geared towards saving both humans and sharks. Sharkdefense does not sell any products, but they are partnered with a company called SharkTec LLC, which sells Sharkdefense approved products at sharktecdefense.com 
Some of the earliest research on shark repellents took place during the Second World War when military services sought to minimize the risk to stranded aviators and sailors in the water. Studies at the time, combined with historical research, revealed that about the only thing that will drive sharks away is the odor of another dead shark. Efforts were made to isolate the active principles in dead shark bodies that repelled other sharks. Eventually, it was determined that certain copper compounds, such as copper sulfate and copper acetate , in combination with other ingredients, could mimic a dead shark and drive live sharks away from human beings in the water. For years, a combination of copper acetate and a black dye to obscure the user was supplied to sailors and aviators of the United States Navy as a shark repellent. Known as "Shark Chaser," it was first packaged in cake form using a water soluble wax binder and rigged to life vests. The Navy employed Shark Chaser extensively between 1943 and 1973. It is believed that the composition does repel sharks in some situations, but not in all, with about a 70% effectiveness rating.
Today, the search for an ideal shark repellent is ongoing. Some research, based on semiochemicals, looks promising. Electrical devices that disturb a shark's sensitive ampullae of Lorenzini are also partially effective.
- Smith, Larry J. (1991). "The effectiveness of sodium lauryl sulphate as a shark repellent in a laboratory test situation". Journal of Fish Biology 38: 105. doi:10.1111/j.1095-8649.1991.tb03096.x.
- Sisneros, Joseph A.; Nelson, Donald R. (2001). Environmental Biology of Fishes 60: 117. doi:10.1023/A:1007612002903.
- Researchers tout shark repellent
- Thomas B. Allen. Shadows in the Sea: The Sharks, Skates and Rays