Why is photosynthesis not the patent of green leaves?

It is not only green leaves that can carry out photosynthesis and deliver nutrition to plants. Plants living on the bottom of the sea-algae, such as brown kelp and dendritic red algae, also contain chlorophyll. Therefore, when sunlight shines on the seabed through the sea surface, they can also carry out photosynthesis like plants on land. The synthetic roots of water chestnut also contain chlorophyll, which can be used for photosynthesis by sunlight transmitted into water.