Fig. 7. Velocity vectors from an asynchronous kick based on a lateral view (vertical light sheet; xy plane). The reference vector equals 1 m s^–1. The four images are separated by 0.04 s, showing the buildup and shedding of the vortex ring generated by the foot. The lower vortex center is shed briefly before the dorsal vortex center, and a discrete vortex ring with a posteroventral central jet flow of high velocity is shed into the water. Free-stream flow velocity has been subtracted from each vector.