Prey detection and identification by white sharks has been studied by the use of experimental baits and objects. The results of these experiments reveal that when white sharks have a choice between a square target and a seal-shaped target, they select the seal shape, as it is more common in their natural environment. When only a single bait was presented, it was regularly investigated. Some scientists believe diver and surfer silhouettes, when viewed from below, resemble those of pinnipeds and that this misidentification by the shark is the cause of most white shark attacks on humans. However, the fact that white sharks attack objects of a variety of shapes, colours and sizes, none of which resemble those of marine mammals, refutes this well-known hypothesis. Researchers suggest that white sharks often strike unfamiliar objects to determine their potential as food. Grasping an unfamiliar object would be the shark's only reliable method of determining whether it is suitable as prey. Great whites prefer energy rich prey, such as marine mammals, rather than less fatty, low energy prey.
White sharks usually swim just below the surface until it is approximately 1 m from its prey and then attacks by turning the head upward and rising out of the water. The white shark also attacks prey with a surface-charge, which is a quick, powerful rush with the body partially above the surface. Occasionally great whites swim with their ventral side up and perform an inverted approach. Their intelligence means they are able to adapt their hunting strategy depending on the prey. In the shallow waters of South Africa they often use stealthy ambush techniques to capture seals. These result in the spectacular breaching scenes when sharks chasing seals in False Bay and Gansbaai take to the air like missiles. White sharks sometimes scavenge from fishermen's nets and long lines. This tendency often results in accidental injury on hooks or in nets.