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, …

A betta fish (Betta splendens) photographed in Lincoln, Nebraska. Also known as Siamese fighting fish, they originally hailed from Southeast Asia but are now popular pets found in …

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 …

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

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.

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 blobfish went viral with this photo, but underwater they look like a completely different fish. They sustain tissue damage when they're brought from the ocean's depths to the surface.

What is a barracuda? Barracuda have a formidable reputation as ruthless predators—even depicted in Disney Pixar’s Finding Nemo as the merciless villain that kills Nemo’s mother. …

This 4-inch-long (10-centimeter-long) fish shares an amazing partnership with another sea creature: the anemone (pronounced: uh-NEM-uh-NEE). The partnership benefits both …

Get your arms around the largest fish in the sea—whale sharks weigh in at up to 60 tons. Find out what tiny creatures keep these gentle giants alive.