Fig. 10. Vertical and horizontal forces acting on a 4.4 cm Lolliguncula brevis swimming tail-first at 15 cm s^–1. In the vertical forces graph, negative values represent forces acting towards the flume floor (i.e. buoyant weight), whereas in the horizontal forces graph negative values represent forces acting in the direction of the free-stream flow (e.g. drag). Since there was some net altitude change over the 2 s video sequence, the height of L. brevis above the flume floor is displayed next to the vertical forces graph. There was no net horizontal change over the video sequence. Fin thrust contributions are not included in the figure.