in geography, a marsh is a type of wetland. it has grasses, rushes, reeds, typhas, sedges, and other herbaceous plants (possibly with low-growing woody plants) in a context of shallow water. a marsh is different from a swamp, which has a greater proportion of open water surface, which is generally deeper than a marsh. in the us, the term 'swamp' is used for wetland dominated by trees rather than grasses and low herbs.