1. White Shark
According to the International Shark Attack File, white sharks were responsible for 403 shark attacks from 1580-2010. One hundred eight-two of these were unprovoked, and of these, 65 were fatal.
Great whites are about 10-15 feet long on average, and they can weigh up to about 4,200 pounds. Their coloration might make them one of the more easily-recognizable large sharks - they have a steel gray back and white underside, and large black eyes.
White sharks generally eat marine mammals such as pinnipeds and toothed whales, and occasionally sea turtles. They tend to investigate their prey by surprise attack, and release prey that is unpalatable. A white shark attack on a human, therefore, isn't always fatal.
2. Tiger Shark
Tiger sharks get their name from the dark bars and spots that run along their side. They have a dark gray, black or bluish-green back and a light underside. They are a large shark, and are capable of growing up to about 18 feet in length and a weight of about 2,000 pounds.
Tiger sharks are #2 on the list of sharks most likely to attack. The International Shark Attack File lists the tiger shark as responsible for 157 shark attacks, 63 of which were unprovoked (and 27 of those were fatal).
Tiger sharks will eat just about anything, although their preferred prey includes sea turtles, rays, fish (including bony fish and other shark species), sea birds, cetaceans (i.e., dolphins), squid, and crustaceans.
3. Bull Shark
Bull sharks are large sharks, prefer shallow waters less than 100 feet deep and are often found in murky waters. This is a perfect recipe for shark attacks, as bull sharks often exist where humans do.
The International Shark Attack File lists bull sharks as the species with the third-highest number of unprovoked shark attacks, with 59 unprovoked attacks (25 fatal) and 26 provoked attacks from 1580-2010.
Bull sharks grow to a length of about 11.5 feet and can weigh up to about 500 pounds. Females are larger on average than males. Bull sharks have gray back and sides, a white underside, large first dorsal fin and pectoral fins, and small eyes for their size (another reason why they may confuse humans with more tasty prey).
Although they eat a wide variety of prey types, humans aren't really on the bull sharks' "preferred prey" list. Their target prey is usually fish (both bony fish, and sharks and rays). They will also eat crustaceans, sea turtles, cetaceans (such as dolphins), and squid.