White sharks are predatory animals that begin life by feeding on fish, rays, and other sharks, and as they grow, switch to feeding on marine mammals and scavenging on large animal carcasses. Their first mammalian prey are usually the small harbor seal, but as the sharks increase in size, they become large enough to eat sea lions, elephant seals, and small toothed whales. Attack strategy consists of a swift, surprise attack from below, inflicting a large, potentially fatal bite. The pinniped often dies from massive trauma or blood loss, but the bites may be superficial or misplaced on the body, allowing the seal to escape and survive the attacks with their scars as witness. Large white sharks will also scavenge on the carcasses of whale sharks, and on the fat-rich blubber layer of dead whales. They will occasionally feed on sea turtles and sea otters, and are known to attack, but not eat, humans.

This shark's behavior and social structure is not well understood. In South Africa, white sharks have a dominance hierarchy  depending on size, sex and squatter's rights: Females dominate males, larger sharks dominate smaller sharks, and residents dominate newcomers. When hunting, great whites tend to separate and resolve conflicts with rituals and displays. White sharks rarely resort to combat although some individuals have been found with bite marks that match those of other white sharks. This suggests that when another shark approaches too closely, great whites react with a warning bite. Another possibility is that white sharks bite to show dominance.

The white sharks are generally very curious animals, display intelligence and may also turn to socializing if situation demands such. At Seal Island, white sharks have been observed arriving and departing in stable "clans" of two to six individuals on a yearly basis. Whether clan members are related is unknown, but they get along peacefully enough. In fact, the social structure of a clan is probably most aptly compared to that of a wolf pack: each member has a clearly established rank, and each clan has an alpha leader. When members of different clans meet, they establish social rank nonviolently through any of a fascinating variety of interactions.

Great white shark attacks on humans are far more likely to take place in the warmer summer months for a number of reasons.

The most obvious are these two:

   1. lots more humans take to the water in summer and

   2. fish prey species return to False Bay and the sharks change their feeding habits and begin to hunt fish   beyond inshore.

- Do not swim, surf or surfski when birds, dolphins or seals are feeding nearby

- Do not swim, surf or surfski near where trek-netting, fishing or spear fishing is taking place.

- Do not swim in deep water beyond the breakers

- Do not swim if you are bleeding

- Do not swim near river mouths

- Do not swim, surf or surfski at night

- Do not swim, surf or surfski if there has been a cetacean stranding nearby

- If a shark has recently been sighted in an area where no shark spotters are present, consider using another beach for the day

- First time visitors to beach areas should ask the local law enforcement official, life guards or locals about the area

- Obey beach officials if told to leave the water

- For those people kayaking or surfskiing far out to the sea, consider paddling in groups and staying close together (in a diamond shape)

- Consider using a personal shark shield when you go surfing or kayaking

- Pay attention to any shark signage on beaches

Source: Wikipedia, and more related articlw.