Sharks have adapted to their habitat by having streamlined, hydrodynamic bodies. Their skeletons aren't made of bone like other fish but cartilage. This makes their skeletons lighter and more flexible.
Like most other fish, sharks are cold-blooded. This gives them a low metabolism and allows them to fast for weeks. However, when it's time to eat, sharks benefit from having short but wide esophagi and jaws that aren't firmly attached to their skulls. This allows sharks to gulp down their prey whole or in large chunks. Sharks' teeth are also replaced constantly.
Sharks' livers, fins and constant movement keep them from sinking. The liver is enormous and filled with a substance called squalene, which helps to keep the shark buoyant.
Sharks also have an astonishing sense of smell and can smell blood in the water as far as one-quarter of a mile away. They also have a tapetum lucidum, a membrane at the back of the eye that lets them see in low light. They can change the size of their pupils to adjust to light conditions, which is an adaptation not found in other fish.
Sharks can also sense electrical fields through organs in their heads called ampullae of Lorenzini.