What do all types of wetlands have in common?

Surface water such as rivers, lakes and oceans. Earth's surface. Wetland plants. Hydric Soils: Wetland soils are different then the soils found in dry.

Wetlands are complex ecosystems that range from marine and coastal areas to continental and artificial areas. Some examples are lakes, mangroves, swamps and also irrigated areas for agriculture, hydroelectric reservoirs, etc.

Answer: the water table (the groundwater level) is very near to the soil surface or shallow water covers the surface for at least part of the year