How Do Fish Breathe Underwater?

💡 Simple Explanation

Fish don't have lungs like us - they have special filters called gills on the sides of their heads. Water has tiny bits of air mixed in called oxygen. When fish swim, water flows in through their mouths and out through their gills. The gills grab the oxygen from the water like catching butterflies with a net! That's why fish open and close their mouths all the time - they're breathing!