(a,b) Pressure contours and flow streamlines at two instants during a propulsive swimming stroke. Left half of body is indicated by black shape. (c,d) Spatial distributions of forward pull (cyan arrows), rearward pull (blue), forward push (magenta) and rearward push (red) due to local fluid pressure. Arrow length is proportional to local pressure magnitude; arrow direction indicates direction of fluid pressure on animal body. Horizontal lines indicate 1 cm scale. (e) Temporal trends of pressure contributions during a jellyfish propulsive stroke. Vertical lines indicate instants corresponding to data panels as labelled. (f) Temporal trends of net pull, net push and net thrust due to pressure on a jellyfish body. Vertical lines indicate instants corresponding to data panels as labelled. Speed of bell apex is indicated by black curve (scale at right). Data represents instantaneous measurements during the swimming of individual animals.