Blue sharks are known for their distinct coloring, which allows them to blend in with ocean water. From above, the water appears darker and camouflages the shark's dark blue back, while its white underside resembles the sunlit ocean surface when seen from below. As a pelagic species, blue sharks inhabit the open water and often travel in large schools made up of only males or females.
The blue shark's body is gracefully contoured for rapid, fluid movement. Its slender form tapers to an elongated tail fin that bends from side to side, allowing it to swim about 35 kilometers per hour on average. Adult sharks often weigh over 240 kilograms and reach up to 4 meters in length.
Blue sharks enjoy a diet of octopus, squid and fish and some species of seabirds, but they are rarely preyed upon by other animals. Their serrated, triangular teeth grow in rows, which are regularly replenished in an eight-day to 10-day cycle.
Female blue sharks have skin that is approximately three times thicker than their male counterparts, preventing extensive injury when they are bitten during mating rituals. These aquatic creatures are pregnant for roughly nine to 12 months before giving birth to live young. An average litter contains 35 pups; as of 2014, the highest recorded number is 135, according to MarineBio.