Fish breath through water with they what?

Fish breathe through water using gills, specialized organs that extract oxygen from the water as it flows over them. Water enters the fish's mouth, passes over the gills, and then exits through openings on the sides of the head. The gills have thin membranes that allow oxygen to diffuse into the fish's bloodstream while carbon dioxide is expelled. This process enables fish to efficiently extract the oxygen they need to survive underwater.