Cat sharks are colorful and exquisitely patterned. The pointed end of these denticles projects toward the tail. These modified scales may overlap or may be widely spaced. In males the pelvic fins are modified into copulatory organs called claspers. Sharks are known for their speed and maneuverability in the water.
Sharks have five to seven gill slits.
Nurse sharks, for example, can lie still and fan their gills to bring oxygen-rich water across the slits. Because they lack a swim bladder, all sharks must swim in order to avoid sinking toward the ocean floor. Sharks have a pointed snout that extends forward and over a crescent-shaped mouth set with sharp triangular teeth. Only a few species, including the white, mako, and tiger sharks, have the large, fearsome teeth popularly thought of as typical of sharks. Shellfish-eating sharks have coarse, pavementlike, crushing teeth.