Fig. 12. Three-dimensional sketches that illustrate the proposed (A) near-fin and (B) far-fin wake of the caudal fin-wave propagation (CFP). The curved black arrows indicate the direction of vortex rotation. (B) The two-dimensional sketch at the upper right illustrates the vortex filaments of the far-fin wake observed on a parasagittal plane. Dashed lines and arrows indicate the vortex filaments and their directions. The feature of the slightly divergent configuration of a CFP jet is not illustrated here.