Seaweeds are simple plants that don’t have flowers. Because they live their life in water, they don’t need to have roots, tree trunks and branches for transporting water to leaves. Often, seaweeds have a base that is glued to rocks or held to the sand.
All plants have green pigment called chlorophyll for converting sunlight into food. Red and brown seaweeds have extra colour pigments for converting sunlight into food.
Green seaweed only has green pigment or chlorophyll for making food from sunlight and is often a strong vivid green. When it is alive, red seaweed is red or pink. Brown seaweed can be olive, green, brown or almost black.
Seaweeds are grouped according to their pigments.
Some flowering plants that look like grass also live in the sea. They are called seagrass and have their roots in the sand.