Synonyms for swamp

bog, fen, quagmire, morass, marsh, slough, soft ground, wet ground, mire, peat bog, holm, swale, bottoms, river bottoms, moor, spongy ground, lowland, bayou, bottomland, cattail swamp, tule swamp, fen land, boggy ground, swampy ground, polder, trembling prairie, Everglades, muskag; see also mud.

Antonyms desert*, high ground, rocky ground.