The shark is a complex collection of senses, each perfectly synchronised with the other. Additionally, the sharks' streamlined shape and powerful muscles make a capable swimmer and formidable opponent. Its skeleton of cartilage is lighter and more elastic than that of a bony fish, enabling it to swim with ease.
 
[ External Features | Senses | Teeth ]
 
 

External Features :

In almost all sharks, the body tapers in front of the tail to form the caudal peduncle. Fast-swimming open-ocean sharks may have one or two lateral keels on the peduncle, which help to reduce water resistance so that much of the shark's muscular power is transferred into the tail fin, which then produces its main thrust in swimming. Examples of different body shapes are shown here.

Most sharks have triangular dorsal fins. There are commonly two, the first often larger than the second, but in some species only one (the posterior, above the anal fin) is present. The leading edge of the dorsal fins may be strengthened with a spine. The pectoral fins are broad based, and located just behind - and in some cases, partly below - the gill slits. As with all the fins in sharks, but unlike the fins of bony fish, the pectoral fins cannot be folded back, and are consequently erect all the time. To a shark, these fish function much as the wings do on an aircraft: cross-sections of the shape of the pectoral fins prove that the design and the effect of both are remarkably similar. With a forward motion, the pressure is increased below and decreased above, thereby lifting the shark without the expenditure of extra energy. The paired pelvic fins are located at about the midpoint of the underside of the shark's body. In males, each fin is modified into claspers, used in mating, which introduces its sperm into the female's genital opening.

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Teeth :
The shark's teeth are its most feared weapons. No other fish has such formidable armory. Row after row of sharp, triangular teeth is the sinister image many people have in their minds of all sharks, even the species like the basking shark, which do not posses any teeth at all. The large hunters, such as the Great White and the tiger sharks, have large, triangular teeth with serrated edges for extra grip and power but some of the smaller species have more pointed, and sometimes curved teeth.

In nearly all species, the teeth point backward, making it impossible for a victim to escape from the mouth. The teeth grow in rows on both jaws and they are continually being replaced from behind, so there are always new teeth ready for those, which are worn or damaged. The jaws of the larger sharks are immensely powerful and combine with the rows of sharp teeth to give it its fearsome bite. Large sharks can slice through the thick shells of fully grown sea turtles and crocodiles, and they can make very quick work of human limbs. 		 

The jaws are not able to make chewing movements, as in grazing mammals, for example, but they are very powerful when opening and shutting. The teeth overlap slightly to produce a strong shearing action. The mouth is normally on the underside of the head, below the snout, but the head and neck are flexible, so the snout can be tilted back and the jaws opened wide to allow the shark to take huge bites out of its victim.