The blue shark has a long, slender body -- up to 12.5 feet -- with a pointed snout. Its upper body is dark blue, the sides are bright blue, and the belly is nearly white. This type of coloration is known as countershading.
The blue shark is a pelagic, or open ocean, shark. It may be seen in offshore surface waters near San Diego and northern Baja Califoria. Its lower jaw is narrow and lined with long, sharp, serrated teeth. It feeds mainly on fish, but it's not shy like its shallow-water or bottom-dwelling cousins, and can be dangerous to open-water divers.
The blue shark is viviparous, and gives birth to live young, or pups. A litter can have as few as four and as many as 100 pups, depending upon the size of the mother.
The blue shark is also called the blue whaler or great blue shark.