An alligator is a whole lot of tail! Full of muscle and strength, the tail makes up half of an alligator’s total length and is designed for efficient swimming.
The tail is laterally compressed (which means it is taller than it is wider) and is topped with tall crests of epidermal scales. This design means it can efficiently propel itself through water… sometimes quite rapidly! The tail moves in a wide, serpentine, side-to-side swishing and a trail of wake and small whirlpools follows a quickly swimming gator.The frequency of undulations increases the velocity of the alligator.
The tail is the primary motor and rudder. According to a study*, it is the “main propulsive effector of surface-swimming.” In fact, while swimming, the limbs are primarily folded along the alligator’s side and contribute little to the thrust and steering.
*Fish, F. E. (1984). “Kinematics of undulatory swimming in the American alligator” (PDF). Copeia. 1984 (4): 839–43.