Aquatic plants have their leaves near or under the water, but they also need to breathe. Plants that float on the surface of the water have their stomata on top, where they have access to air. Plants that live completely under water gather carbon dioxide from the water.
That sounds really new to me. Aquatic plants are also like fish. They are already used in the water. They can live without air and fertilizer just water?
They do not need it because of their design to live in the water. Aquatic plants possess a lot of spongy cells full of air which helps them float on surface of water. These cells are called aerenchyma.