An obvious performance advantage of the shark tail morphology
is the contribution of the radialis muscle to continuous thrust
generation. While not all shark species exhibit life histories necessitating
long distance migrations or the capture of fast-swimming
prey, they all profit from a metabolic advantage to continuous
thrust production. When a fish swims, drag on the body causes
deceleration whenever itis not producing thrust. Then, when thrust
is produced, momentum created must overcome the inertial mass
of the body in addition to providing forward propulsion. If the body
does not decelerate between tail beats, then the momentum continuously
drives the fish forward, thereby facilitating increases in
velocity.