The slippery world of seaweed

• Seaweeds belong to a group of simple plants called algae. Plants need light to grow, so seaweeds must live around the seashore or float near the top of the water where there is sunlight.

• Seaweeds can be flat, soft, slippery, leafy or stringy. They cling to rocks with 'holdfasts' that look like roots. Some have air pockets to help them float. Giant kelp forms tall underwater forests that grow up to the light.

• Seaweeds are very useful. Many sea creatures eat seaweed, and people can east most of them too, if they are clean. We use seaweed as fertiliser to feed plants, and in products like medicines. Seaweeds also make oxygen for us to breathe.