湖沼[koshou] lakes and marshes
沼沢[shoutaku] marsh
沼地[numachi] marshland
ドロ沼[doronuma] bog
沼田[numata] marshy rice field or paddy

沼気[shouki] marsh gas
沼湖[shouko] marshes and lakes
池沼[chishou] ponds and swamps
沼杉[numasugi] bald Cypress (Taxodium distichum)

井の中の蛙大海を知らず[inonakanokawazutaikaiwoshirazu] parochial
雨蛙[amagaeru] tree frog (esp. the Japanese tree frog, Hyla japonica)
蛙の子は蛙[kaerunokohakaeru] like father, like son
蛙跳び[kaerutobi] (game of) leapfrog
殿様蛙[tonosamagaeru] black-spotted pond frog (Rana nigromaculata)

蟇蛙[hikigaeru] toad (esp. the Japanese toad, Bufo japonicus)
蛙又[kaerumata] curved wooden support on top of the main beam of a house, now mainly decorative (shape evocates an open-legged frog)
青蛙[aogaeru] green (tree) frog
赤蛙[akagaeru] any brown or reddish-brown frog (esp. of family Ranidae)