We have a bacKBone and we breathe by using our gills to take oxygen from the water. Our gills are located behind our head.

We have fins and a tail to help us move through the water, change direction and stay upright. Most of us have scales to protect us from damage and things like sunburn and germs.

Most of us have a swim bladder that helps us float in the water.

On the inside we have organs just like you - a heart, liver, kidney, brain and intestines - just a lot smaller. Imagine a jelly bean and you have roughly the size of the heart of a fish about 25 cm long.

We live in water that is fresh, salty or brackish, which is a mixture of both fresh and saltwater.

Most of us are cold-blooded, which means our temperature goes down when we're in cold water, and rises in warm water.

We eat plankton, shrimp, shellfish and, yes, we can even eat other fish. Some of us also eat seaweeds and other plants.

Like you, we need rest. We can't close our eyes but we can slow down, and 'sleep' by staying very still.

Biologists can tell how old we are by counting the growth rings on our scales or earbones.

Want to know more about fish? The Australian Museum Fish Site has answers to lots of Frequently Asked Questions.

Crustaceans, such as prawns, crabs and crayfish, are called invertebrates, which means 'not having bacKBones'.

Sharks are fish. Read about the grey nurse shark.

Find more facts about fish under Did you know?