How do fish breathe?

Answer 1

they breathe water
Via the gills, by osmosis. The oxygen they need is dissolved in the water.
Fish extract the oxygen out of the water using their gills, thus leaving the water hydrogenated, which some plants and animals (marine ones) need as opposed to oxygen so balance is restored. Hope this helps.
Fish breathe underwater using their gills.
Fish "breathe" by gulping down water. This water passes over the fishes' gills, made up of the same flesh as our lungs (roughly), which extract the water using either active transport, or simply a concentration gradient on a partially permeable membrane, I'm not quite sure. Either way, the oxygen is extracted from the water, and Carbon Dioxide replaced. The water then passes out the slits in the side of the fishes head.

This method is very effective, meaning the fish can extract around 80% of the oxygen in water, which is EXTREMELY important, as water only contains 2-5% oxygen, as opposed to 20-something% for air.

Also, the ease of which the oxygen is extracted depends on the water temperature, whether it is salty, and other factors. This is why most Freshwater Fish can't survive in the ocean.

Answer 2

Fish breathe by extracting oxygen from the water through their gills. As water passes over the gills, oxygen is absorbed into the fish's bloodstream and carbon dioxide is released. This process allows fish to extract the oxygen they need to survive in their aquatic environment.

Answer 3

they breathe through gills.They breath in then out then in then out through something called "gills" and guess what? Fishes also have a brain maybe you might have one to.