Instead sharks have a large liver that has a specific gravity of 0.926, sea water has a specific gravity of 1.025, which gives them neutrally buoyancy. The shark also has another feature that gives it positive buoyancy, it's large pectoral fins. These fins behave like large wings providing the shark with lift. A special type of shark, the hammerhead shark can also use its head, since it is flat and broad, to provide it with lift. Senses - Sharks have a multitude of senses to seek out and capture their prey.
Sharks have a remarkable sense of smell, to detect even minute amounts of blood in the water.
Sharks have a sensory device, the ampullae of Lorenzini, that sense out electrical fields. They use this sense to tract and locate injured, thrashing, prey and to aid in navigation. Sharks also have good eye sight, and hearing. If you add up all of these sense they equal one magnificent predator. Sharks are amazing and magnificent creatures, who through million of years of evolution have clearly risen to be the apex predator of the sea.