Kelps are found in cold waters throughout the world. They do not grow in tropical waters.
Kelps vary widely in size and form.
One type of kelp, called giant kelp, may have hundreds of branches, each of which has hundreds of leaves. In areas where many giant kelps are found together, they form underwater forests. Many marine animals, such as snails and sea urchins, feed on kelps. Other animals, including lobsters and many fish, use kelps for shelter. People in China and Japan grow kelp for food on special farms in the ocean.