Beach lovers may lament the odd jellyfish sting, but scientists say the critters really do suck - and it makes them very efficient ocean swimmers.
While most animals generate thrust by pushing water backwards, jellyfish and lampreys pull themselves through water by creating low pressure regions in the fluid around them, which effectively sucks them along, US researchers say.
Stanford University's John Dabiri and his colleagues made the findings after studying the movements of lampreys and jellyfish as they travelled through tunnels where the water had been "seeded" with small glass beads to allow the motion of the surrounding fluid to be traced.
Scientists hope the knowledge about the efficient swimmers will help with the design of future underwater vehicles.
