How do sharks use their tails for swimming?

Sharks, which belong to the class Chondrichthyes, utilize their tails primarily for powerful, fast swimming through undulatory movements produced by their axial musculature. These muscles, which make up a significant portion of the shark's body weight, create waves of contraction that travel along the body and the caudal (tail) fin to generate thrust.1

Most sharks possess a heterocercal tail, a structure where the vertebral column extends into the larger upper lobe of the fin. Beyond general locomotion, some species have evolved specialized uses for their tails. For example, the thresher shark uses its exceptionally long, scythelike tail to stun or frighten prey by thrashing the water. While the tail provides the primary thrust for speed, other fins, such as the dorsal and paired anterolateral fins, are essential for stabilization and steering to prevent unwanted rolling, pitching, or yawing during movement.234