<P> Many sharks, including the whitetip reef shark are cooperative feeders and hunt in packs to herd and capture elusive prey . These social sharks are often migratory, traveling huge distances around ocean basins in large schools . These migrations may be partly necessary to find new food sources . </P> <P> Sharks are found in all seas . They generally do not live in fresh water, with a few exceptions such as the bull shark and the river shark which can swim both in seawater and freshwater . Sharks are common down to depths of 2,000 metres (7,000 ft), and some live even deeper, but they are almost entirely absent below 3,000 metres (10,000 ft). The deepest confirmed report of a shark is a Portuguese dogfish at 3,700 metres (12,100 ft). </P> <P> In 2006 the International Shark Attack File (ISAF) undertook an investigation into 96 alleged shark attacks, confirming 62 of them as unprovoked attacks and 16 as provoked attacks . The average number of fatalities worldwide per year between 2001 and 2006 from unprovoked shark attacks is 4.3 . </P> <P> Contrary to popular belief, only a few sharks are dangerous to humans . Out of more than 470 species, only four have been involved in a significant number of fatal, unprovoked attacks on humans: the great white, oceanic whitetip, tiger, and bull sharks . These sharks are large, powerful predators, and may sometimes attack and kill people . Despite being responsible for attacks on humans they have all been filmed without using a protective cage . </P>

Do great white sharks only live in saltwater