Meet the real "Nemo," the colorful clownfish. Find out how these fish can reproduce even though all their young are born male.

A whale shark the size of a school bus swims slowly near the surface of the ocean. Its wide mouth is open, like an enormous net scooping up whatever happens to be around—mostly small fish, fish …

Freshwater makes up less than 3 percent of Earth’s water supply but almost half of all fish species live in rivers, lakes, ponds, and wetlands.

Sharks star in blockbuster movies as blood-seeking villains, but in reality they’re far more fascinating and complicated than they’re often depicted in pop culture. Based on fossilized teeth ...

Pufferfish can inflate into a ball shape to evade predators. Also known as blowfish, these clumsy swimmers fill their elastic stomachs with huge amounts of water (and sometimes air) and blow …

The alligator gar bears no relation to alligators, but with its wide, crocodilian head and razor-sharp teeth, it’s easy to see how this giant fish got its name. The largest of seven known gar ...

Jellyfish have drifted along on ocean currents for millions of years, even before dinosaurs lived on the Earth. The jellylike creatures pulse along on ocean currents and are abundant in cold and warm …

There are many breeds of goldfish (Carassius auratus). This is a celestial eye goldfish, which has large eyes turned upward.

Discover the incredible anglerfish, denizen of the ocean's deep, lightless realms. Learn how these predators attract their victims with bits of luminous flesh.

Find out how these "blowfish" defeat predators by puffing up into inedible balls. Learn how their potentially lethal toxins provide another line of defense.