Fig. 3

White shark Tail beat signal. The peak frequency of the tailbeat (a) should be consistently detected in the horizontal plane (swaying acceleration) measured by the X and Y axes (blue and red, respectively; see Fig. 1a) near 0.4 Hz or 2.5 s. Rotating the coordinate system about the Z axis (b) the tail beat frequency power is maximized along the X and Y axes at perpendicular angles. The desired coordinate orientation was reached where power peaked along the Y axis