Here's a good little video ...
https://www.youtube.com/watch?v=HRmexiPYnu4
Generally speaking, a shark has one of three forms
Lamnid - these sharks have conical-shape noses, tails with equal-sized lobes, and heavy bodies. They swim with a distinctive stiff manner. Their body temperature is higher than the surrounding water, making these animals efficient swimmers in cooler waters. The Great White Shark (Carcharodon carcharias) is a typical example.
Carcharhinid - these sharks have blunt, flat noses and tails with a longer upper tail fin. This long upper tail fin drives the head downward, whilst the broad, flat nose acts like an aquaplane, keeping the head up and allowing the shark to swim through the water. These sharks often have flexible bodies and can twist and turn to chase prey. The Tiger Shark (Galeocerdo cuvier) is a good example.
And Benthic (bottom-dwelling types) - these forms are typically sluggish in comparison to the above types. These species often have the ability to pump water over their gills, allowing them to rest on the bottom and breathe. The Great White cannot do this - it must keep swimming in order to breathe. The Port Jackson Shark (Heterodontus portusjacksoni) is a good example of a bottom-dwelling species.