Water (aquatic) plants are plants that have adapted to living in aquatic environments. They are also referred to as aquatic macrophytes. A macrophyte is an aquatic plant that grows in or near water and is either emergent, submergent, or floating. In lakes macrophytes provide cover for fish and substrate for aquatic invertebrates, produce oxygen, and provides food for some fish and wildlife.

Aquatic plants are unique because they require special adaptations for living submerged in water, or at the water's surface. These plants can only grow in water or in soil that is permanently saturated with water. Aquatic vascular plants have vascular tissues, which circulate resources through the plant. This feature allows vascular plants to develop to a larger size than non-vascular plants, which lack these specialized conducting tissues and are therefore restricted to relatively small sizes. Seaweeds are not vascular plants; rather they are multicellular marine algae, and therefore are not typically included among aquatic plants. This type of plant does not have a problem retaining water, due to the abundance of water in their environment. This means there is less need to regulate transpiration, a process similar to evaporation, which would require more energy and be of little benefit to the plant.

Aquatic plants have certain distinguishing characteristics, such as:

1. A thin cuticle. Thick cuticles reduce water loss, thus aquatics have no need for thick cuticles.
2. Stomata that are open most of the time due to the abundance of water and there is no need for it to retain in the plant.
3. An increased number of stomata, which can be on either side of the leaves.
4. A less rigid structure, water pressure supports them.
5. Air sacs for flotation
6. Flat leaves on surface plants for flotation.
7. Small roots because the water can diffuse directly into the leaves. Large root systems are not required for water intake.

Many species of aquatic plant are invasive species. Aquatic plants make particularly good weeds because they reproduce vegetatively from fragments.

We all are very familiar with the water hyacinth, a free-floating perennial plant native to tropical and sub-tropical South America. The hyacinth has broad, thick, glossy, ovate leaves, and may rise above the surface of the water as much as 1 meter high.

It is one of the fastest growing plants known, reproducing primarily by way of runners which eventually form daughter plants. Also, large quantities of seeds are produced and they are viable up to 30 years. The common water hyacinth are aggressive growers known to double their population in 2 weeks.

A bit of trivia for your next game:

In Southern Pakistan they are the provincial flower of Sindh.

In the Philippines, enterprising individuals use some of the water hyacinth's stems and dry it to take its fibers and take them to form strands of string. This string is woven or interlinked together to form a hemp used for making bags, footwear, wreaths, hats, vases, Christmas lanterns and other decorative items. Since the water lily is in abundance, a nuisance to some, lets individuals earn money by selling these items and indirectly aids in cleaning up the overpopulated bodies of water that are full of water hyacinths.