Water is one of the basic requirements of life. This is why areas close to water are often greener than other places. A large variety of different plants grow near the water.

Some of these plants grow near to the water’s edge. Other plants grow on the water's surface or partially under it. The leaves of aquatic plants can be located above the water, on its surface, or under the water. 

Plants produce energy through the process of photosynthesis. Photosynthesis requires sunlight. As a result, plants try to grow and spread their leaves in a way that allows them to catch as much sunlight as possible. The deeper we move in the water, the less sunlight there is. Because of this, the number of plants decreases steadily when we move deeper in the water, and the deepest areas are completely free of plant life.

In addition to sunlight and water, plants also require warmth. In Finnish conditions, plant growth is often limited by the cold temperatures and ice layers that form during the winter months. No photosynthesis can take place in cold water. As a result, plants do not grow if the conditions are too cold.

Plants also require nutrients such as nitrogen in order to grow. In flowing water, such as a river, the amount of nutrients is often small. As a result, plant life is less numerous in rivers than in lakes and ponds.

In small ponds, the water turnover is minimal. As a result, they often accumulate large amounts of nutrients. This causes rapid plant growth. When this happens, plant leaves can quickly cover the whole surface of the pond.