Why cant fish breath above water?

When I looked at this diagram of the inside of a fish I saw gills but not lungs. I also read that the gills are only designed to take the oxygen out of water and we cant filter water we just breathe in air.(The fish take the oxygen molocule of H2O). The fish don't take all the oxygen out of the water. They take only the oxygen molocules out of the water they took in. Then, they release CO2 in to the water and plants like seweed take it in and produce more oxygen for the fish to breath.

COOL PICTURE OF INSIDE OF A FISH HEAD!