Marshes, swamps, tidal flats and associated pools, bayous, and bogs are the most common. Marshes are water-saturated, poorly drained areas with both aquatic and grasslike plants. Swamps, unlike marshes, have trees and bushes. Water flows into swamps and marshes from streams, or even an ocean. Bogs are waterlogged, spongy ground in former lakes now filled with living and dead mosses, which eventually become peat.
Wetlands are important for many reasons.
They support a large volume of plants, which in turn supply cover and food for animals. Wetlands retain water like a giant sponge - flowing water is slowed as it passes through and is absorbed by plants and soils. By soaking up the water, wetlands not only prevent floods but make water available during a drought. They also help reduce the threat of low salinities in coastal waters. Wetlands can also clean up contaminated water.