Here is a great image from wikipedia on its distribution around the world:
http://en.wikipedia.org/wiki/Image:Carcharhinus_leucus_distmap.png
The bull shark has a short snout that is wider than it is long (hence its name). Its belly is off-white, its top surface is gray, and the eyes are small. The first dorsal fin is much longer and more pointed than the second dorsal fin. A pup's fins have black tips, but these marking fade in the adults. The females are larger than the males. Bull shark teeth are triangular, serrated (saw-edged), and very sharp.
The bull shark is found close to shore and can live for a while in fresh water, frequenting estuaries, rivers and lakes. It has been found up to 1,750 miles (2800 km) up the Mississippi River in the USA and 2,500 miles (4000 km) up the Amazon River in Peru. It has been found in Lake Nicaragua (Central America) and the Zambezi River (Africa). The bull shark eats fish (including other sharks and rays), turtles, birds, mollusks, crustaceans, and dolphins. It will eat almost anything. It is one of the most often attacker's of people, as it swims in very shallow waters where people swim and is an aggressive shark. And it often swims far up brackish and even fresh rivers that have a saltwater outlet so it will show up where least expected.