<P> Aquatic respiration is the process whereby an aquatic animal obtains oxygen from water . </P> <P> In most fish respiration takes place through gills . Lungfish, however, possess one or two lungs . The labyrinth fish have developed a special organ that allows them to take advantage of the oxygen of the air, but is not a true lung . Fish use the process known as countercurrent flow, in which water and blood flow in opposite directions across the gills, maximizing the diffusion of oxygen . </P>

Where does sea water fish get their supply of oxygen