A water garden is very popular for landscapes, particularly in Asian cultures. A wide variety of water, or aquatic, plants are available, other than the usual water lilies or bamboo. Keep many considerations in mind though, such as the depth of your water, how much sunshine is available at the location and if you'd like flowers or just vegetation. Ideally, your water garden will have not just floating plants but submerged ones as well. Water plants are split up into three categories: emergent, submerged and floaters.
Emergent, otherwise known as marginal, water plants are the type of vegetation that grows along the water's edge. Usually the roots are secured to the bottom and the stems are what floats above water, in shallow and in deep areas. Common emergent water plants include cattails, lotus, iris, water lilies and pickerelweed. Bog plants are also considered to be emergent plants and are ideal for shaded ponds since they only need about three hours of sunlight per day. Bog plants include species such as dwarf bamboo, sweet flag and sagittarius, to name a few. Emergent plants have leaves that are most similar to plants that thrive on land.
Use submerged plants such as ponds weed, elodea, water nymph and ditch grass to add foliage underneath the water's surface. This benefits the overall health of the body of water, as they act as oxygenators, provide shelter for fish and battle algae. Since the roots are only used for anchoring the plant, they can be planted in rocks if needed. The leaves on submerged plants are very thin and flexible.
Floaters are plants that are not rooted at all in the pond and float openly on the surface to take advantage of full sun exposure (so they need a lot of daily sun). These help add a beautiful polished touch to a water garden and act as groundcover for water, particularly if the floaters have blooming flowers. Since many floaters actually do shift around on the water's surface, it can provide an architectural change to the water garden. These aquatic plants usually have broad leaves that are firm and flexible. Popular floater plants include floating heart, Victorian water lily, frog bit, water-shield, duckweed, water hyacinth and water lettuce.