Fish
Fish are usually covered with scales, and have two sets of paired fins, and several unpaired fins. They are usually cold-blooded. A fish takes in the oxygen from the water using gills. There are many different kinds of fish. They live in fresh water in lakes and rivers, and in salt water in the ocean. Some fish are less than one centimeter long. The largest fish is the whale shark, which can be almost 15 meters long and weigh 15 tons. Most fish live in the water. A group of fish called the Lungfish have developed lungs, because they live in rivers and pools that dry up, certain parts of the year.