When you and I take a deep breath, we pull air into our lungs. That’s because humans are mammals. But fish aren’t mammals. They usually don’t breathe air. They usually don’t have lungs. That’s what I ...

Most people assume that fish are perfectly safe underwater and that drowning is impossible for them. After all, they are uniquely designed for life beneath the surface. But the idea that fish cannot ...

Fish live surrounded by water, so the idea that they might struggle to breathe sounds wrong at first. It feels like asking whether birds can fall out of the sky. Still, the question keeps coming up, ...

Add Yahoo as a preferred source to see more of our stories on Google. Your blood's natural limit to how much oxygen it can hold means you can't stockpile it. Lisa520/E+ via Getty Images You need to ...

Oxygen shaped the world as we know it. It’s why we hiccup and why frogs croak. It’s so good that some turtles have learned to suck it in using not just their nose and mouth, but also… another orifice.

Nighttime drops in ocean oxygen raise energy use in small reef fish. Repeated stress could affect reef health as oceans warm.