🐟 Fish

Fish live in water and breathe it through gills. They swim with fins, and most are covered in scales. Sharks are fish too. Whales and dolphins are not: they breathe air.

The biggest and the smallest here: the whale shark and the clownfish

🧒 our measuring child, 4 ft1.2 m🦈 Whale shark, 40 ft12.2 m long🐠 Clownfish, 3.5 in9 cm long🔍 Pip the pangolin zoomed in 50 times on the clownfish

⚖️ Compare them

What makes a fish?

They live in water their whole lives.
They breathe water through gills.
They swim with fins, and most have scales.
Most lay eggs in the water.

10 animals here

Record holders here

Fastest: the sailfish, 68 mph109 km/h1
Heaviest: the whale shark, 40 tons36 tonnes2
Lives longest: the whale shark, 60 to 100 years60 to 100 years2

Fish for kids, A to Z

🐟 Atlantic bluefin tuna: A huge, speedy fish that crosses the whole Atlantic Ocean.
🐠 Clownfish: A small fish that lives safe inside the stinging tentacles of an anemone.
🐟 Giant manta ray: The biggest ray, gliding through the sea on wide, wing-like fins.
🦈 Great white shark: The biggest fish that hunts, with rows of spare teeth waiting.
🐟 Lined seahorse: The dad seahorse carries the eggs in a pouch on his belly.
🐡 Ocean sunfish: The heaviest bony fish looks like a swimming head and eats jellyfish.
🐟 Red-bellied piranha: A fish with sharp teeth that is much shier than the stories say.
🐟 Sailfish: A speedy fish with a tall back sail and a long, pointed bill.
🐟 Sockeye salmon: A fish that swims home to the very river where it hatched.
🦈 Whale shark: The biggest fish alive is a gentle shark that eats tiny food.

NOAA National Ocean Service, Ocean Facts feed ('What is the fastest fish in the ocean?'), checked 30 October 2026.
NOAA National Ocean Service, checked 30 October 2026.