The Dusky Shark

  Dusky sharks are a species of requiem shark and they an grow to 4.2 metres (14 feet) long. They spend most of their time in the sunlight zone, but have been recorded to dive as deep as -400 metres. A single dusky shark can migrate from under two hundred to over a thousand kilometres a year in search of food.
  Dusky sharks can be found all over the world. They are common off the shores of Australia, Southern Japan and South Africa. They can also be found in the Atlantic Ocean on the shores of North, Central and South America. However, marine biologists suspect that they can also be found in the Mediterranean Sea in addition to the coasts of West Africa and Spain.

The dark blue shows the dusky shark's recorded range.
The light blue shows the dusky shark's suspected range.

  Dusky sharks are not as prolific feeders as their requiem opportunist counterparts like tiger and bull sharks, however, they are known to scavenge when they reach full maturity (around 20 years of age) and can be found tearing into the flesh of a dead whale amongst other more impressive specimens such as great whites and a group of three or for of them will decimate a porpoise or manatee carcass in seconds. Their bite force of a dusky shark is 60 kilograms per tooth, the equivalent of being crushed by ten cars, is a large contribution to their ability to crack through turtles shells.
  The diet of a dusky shark mainly consists of tuna, mackerel, bluefish and herring. But larger dusky sharks have been known to eat turtles, guitarfish, stingrays,  angel sharks, thresher sharks and dogfish. These sharks really have big appetites!!

A dusky shark in Sea World Queensland, Australia.

A dusky shark swimming in the Pacific Ocean.

Last year, a man wrestled a dusky shark in an attempt to get it away from a group of children. This video is professional footage of the struggle. Do not bother watching beyond 40 seconds as  the shark is not featured beyond that point.
http://www.youtube.com/watch?v=c9Dr1mcpoEA