Great Blue Heron in a wetland. Photo by Tyler Butler on Unsplash

Wetlands are areas that are totally or partially covered with water. They are transitional between permanently flooded deep water areas and areas with their water tables near the surface. Sometimes, shallow water covers the surface of the land. Examples of wetlands are:

brackish marsh,
fresh marshes,
salt marshes,
swamps,
wet prairies,
bogs,
forested wetlands,
and vernal pools. 
You can also refer to wetlands as areas with dominant natural water saturation levels, determining the soil development processes and the plants and animals inhabiting them. The covering of water in some wetlands could be permanent or seasonal.