Example video, flow patterns, and kinematic variables during steady swimming at 1.5 BL s-1. The top panel shows video, filmed from below, with flow vectors in color. The color indicates vorticity. The bottom two panels show the fish’s relative speed within the flow tank (white solid line), the acceleration (brown dotted line), the position of the tail (blue dashed line), and the absolute value of the circulation of vortices shed into the wake (red circles). The current time within the video is shown with a dashed white line, and the time that corresponds to Fig. 3A is shown with a dotted white line. The video is slowed by 10 times.