Over the years, experts have been trying to determine exactly why great white sharks attack humans. Three of the main theories include the investigatory theory, mistaken identity theory and social-defensive theory.
When it comes to the investigatory theory, great white sharks are curious about their habitat. Whenever they sense unknown objects on the water, they investigate them. If they can't determine what the object is, the sharks bite the object in an investigatory manner. However, instead of an object, it could actually be a person that the shark is biting.
Sharks are able to sense humans in the ocean before humans can sense a shark nearby. Great white sharks can smell objects from up to hundreds of meters away. Many attacks occur because of poor water conditions when the great white sharks can't see or hear as well. Therefore the sharks mistake humans for the normal prey that they consume. This is a case of mistaken identity theory.
The social-defensive theory is based on the fact that great white sharks are known to defend their personal space by biting and posturing. If somebody is swimming or surfing, the sharks view the person as competition for fish in the water.