Great white shark
Usually in a shark attack, the shark bites the human once and then swims away for a while.  Sometimes the shark will bite off a leg or arm, but usually the bite is just a bite. Sometimes there is no tissue loss at all (nothing bitten off). Deaths in such cases are generally caused by loss of blood from the first wound. In cases where attacks have occurred and the victim has been unable to escape quickly, partial or whole consumption has occurred; lone divers are especially at risk of this. Scientists are not sure why this is but they have some ideas.