White sharks are known to be cannabilistic and will raise their heads above the surface to, it is believed, analyze the location of prey, by smell. But it depends on the type of prey.
White sharks have a variety of shark attack moves in their predatory arsenal. They are of course, carnivorous and eat mainly fish, though they will eat dolphins, porpoises, whale carcasses, seals, fur seals, sea lions and sea turtles. Mainly, they prefer prey with high levels of energy-rich fat.
The Great White shark is an Apex Predator. Meaning it is at the top of the food chain, not normally hunted by other predators within its own environment and it is a vital entity of eco-system health.
Whereas Great White's were once thought of as maniacal eating machines, it is now known that they actually are thinking hunters and will ambush their prey. In South Africa's False Bay, studies have concluded that the Great White sharks dive deep, very early in the morning and begin their ambush attacks about 2 hours after sunrise. They will have a clear view of their prey and their prey will not see them coming. This is how they hunt fur seals off Seal Island, South Africa. After hitting the seals at midsection, stunning the animal, they then proceed with the meal. Sometimes, the shark is traveling upwards at such a high rate of speed that they actually shoot up out of the water.
Larger elepant seals which can be as large as a Great White shark are attacked and bitten from behind and allowed to bleed to death before the meal begins.
Scientists who've studied the Great White shark over the past 25 years have come to the conclusion that they prefer pinnepeds, other wise known as sea lions, otters and seals, as the shark matures.
Harbour seals are bitten and dragged down until they stop struggling.
Dolphins are equipped with echolocation naturally, and somehow the shark knows this. The Great White will attack the dolphin from below, above or behind.
When the waters are very warm due to El Nino, Great White sharks are more abundant off central California coasts due to a northern shifting of their prey. A common feeding ground for the Great White is around the Ano Nuevo State Reserve and the Marin Headlands.
It is said that Great Whites will bite humans but will not eat them.
*It is interesting to note that it has actually happened where dolphins have ganged up on one shark and bludgeoned it to death with their noses.
Sources: Wikipedia.org www.ucmp.berkeley.edu