Fig. 3. Kinematics of a cyclically swimming zebrafish larva (age 3 d.p.f., body length L=3.8 mm). (A) The larva generates a body wave travelling down its body with a roughly constant tail-beat frequency and amplitude. Blue, path of the head, red, path of tail. (B) The body wave becomes prominent behind the stiffer anterior body and travels as a wave of curvature with a roughly constant speed along the posterior body. (Same sequence as Fig. 4.)