The blue shark's snout is longer than the width of its mouth. Its pectoral fins are extraordinarily long, approximately the length from the tip of the snout to the last gill slit. The upper teeth are triangular, curved cusps with serrated edges and overlapping bases. Lower cusps are erect and smoother.
Color above is a deep indigo shading to a brighter blue on the sides.
The undersides are white. Reproduction Blue sharks are viviparous and thought to be the most prolific of the larger sharks. Usually 25-50 pups are born per litter and up to 135 have been reported. Their gestation period lasts 9-12 months. The pups measure 40-51 cm at birth.