Propulsion of a small (~5 mm) species of jellyfish that cruises as fast as or faster than most predatory bony fish, when measured in body-normalised units (that is, greater than 10 body lengths per second). The flow visualization of the wake recveals successive vortex rings. The first video shows a closeup of a valve-like flap on the animal body that interacts with the vortex ring during its formation. The second video shows the wake. The videos were captured at 250 fps and are played back at 15 and 30 fps, respectively.