Both humans and fish breath the same oxygen that’s in the air. But the difference is that fish get their oxygen from the water. How? They have sets of thin flat lacy things called gills instead of lungs! They suck water into their mouths and then push it out through these gills which are located on either side of their mouth. As the water flows out, their gills pick up the oxygen in water so they can breath. That’s pretty clever, eh? But, then, listen … fish can’t sunbathe the way you humans can.