Wet prairies are slightly elevated like sawgrass marshes, but with greater plant diversity. The surface is covered in water only three to seven months of the year, and the water is, on average, shallow at only 4 inches (10 cm) deep.[53] When flooded, the marl can support a variety of water plants.[54] Solution holes, or deep pits where the limestone has worn away, may remain flooded even when the prairies are dry, and they support aquatic invertebrates such as crayfish and snails, and larval amphibians which feed young wading birds.[55] These regions tend to border between sloughs and sawgrass marshes.