Do Fish Have Lungs? Explained with Helpful Infographics

No, fish don’t have lungs — at least not most of them. Instead, they breathe through gills, which are specially adapted to pull oxygen from water, not air. It’s one of those amazing examples of how animals are built perfectly for their environments.

Let’s break it down in a simple, real-world way — the way I had to when a curious kid once asked me why fish don’t drown!

How Fish Breathe (And Why It’s Not With Lungs)

Fish take in water through their mouths and push it out through their gills, which are like thin, blood-filled filters. As the water flows over the gills, oxygen moves into the bloodstream, and carbon dioxide moves out — kind of like how our lungs work, just with water instead of air.

What’s especially cool is that the blood in the gills moves in the opposite direction of the water flow. This counter-current exchange helps the fish absorb as much oxygen as possible — a neat bit of natural engineering.

And no, fish gills don’t have alveoli like our lungs do. The gas exchange happens directly through those thin gill walls, without needing the cup-shaped air sacs we have.

What About Dolphins and Whales?

This is a common mix-up. Dolphins and whales may live in the water, but they’re mammals, not fish. They have lungs and need to surface regularly to breathe air through blowholes. That’s why you’ll often see them leaping out of the water — they’re not just showing off, they’re literally catching their breath.

Are There Any Fish With Lungs?

Yes, but they’re rare. Lungfish are the big exception. These freshwater fish do have real lungs and can breathe air. In fact, some can survive out of water for a while, especially when rivers dry up — they’ll burrow into mud and wait for better conditions. There are only six species of lungfish left today, found in Africa, South America, and Australia.

The Australian lungfish is a bit unique — it has only one lung, while the others have two.

What About Swim Bladders?

Swim bladders (or air bladders) are another interesting feature in many bony fish. These are gas-filled sacs that help fish control their buoyancy — basically, they’re like built-in floaties.

Some of these bladders can absorb a bit of oxygen when fish are young and still able to gulp air from the surface. But as the fish grow and that connection to the surface closes off, the bladder becomes more about floating and less about breathing.

So while they sound a little like lungs, swim bladders aren’t meant for breathing and don’t allow fish to survive out of water.

Quick Recap

• Most fish don’t have lungs — they breathe with gills.
• Gills pull oxygen from water, not air.
• Dolphins and whales have lungs but aren’t fish — they’re mammals.
• A few rare fish, like lungfish, actually do have lungs and can breathe air.
• Swim bladders help with floating but aren’t true breathing organs.

It’s fascinating to see how nature has come up with different ways for animals to get the oxygen they need. Whether it’s gills in fish, lungs in mammals, or something in between, every creature has its own clever solution for staying alive.