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. Testing and research The original "SharkPOD" was tested for eight years off Dyer Island with mainly great white sharks, and was the first electronic device that was proven successful in deterring sharks when tested by Ron Taylor and Valerie Taylor in 1997 against great white sharks, tiger sharks, hammerhead sharks, and other shark species in Australia and South Africa with positive results; they made a documentary about it called "Shark POD". In 2003, C F Smit, Department of Statistics, University of Pretoria, South Africa and V Peddemors, Department of Zoology, University of Durban-Westville, South Africa (Peddemors was employed by the Natal Sharks Board at the time) researched "Estimating the Probability of a Shark Attack when using an Electric Repellent". In two series of tests of the SharkPOD, data were collected on the time needed to attack the bait, under power-off and power-on (active) conditions. Conclusions were separately drawn after completion of the first experiment (in which 8 attacks were successful in 98 five-minute active periods), and after completion of the second experiment (in which no successful attacks were recorded in 24 ten-minute active periods). In general, the probability of an attack in at most 5 minutes was reduced from about 0.70 in power-off mode to about 0.08 in power-on mode and in a period of at most