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 aquariums around ...

Meet the newest ‘walking’ fish—a bright red creature of the deep This odd-looking sea toad may look like crochet. But it's one of a hundred species possibly new to science that have been ...

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 …

Sharks can rouse fear and awe like no other creature in the sea. Find out about the world's biggest and fastest sharks, how sharks reproduce, and how some species are at risk of extinction.

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.

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

Soar into the world of flying fish. Find out how their amazing talents—that may be used to avoid predators—can sometimes get them in trouble.

Taking a blobfish out of water is like “heating something that’s glued together and the glue starts to melt.” The blobfish went viral with this photo, but underwater they look like a ...

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

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 ...