滩涂 (tān tú) refers to intertidal mudflats—low-lying, soft-sediment coastal areas that are submerged at high tide and exposed at low tide. The character 滩 means 'beach' or 'shoal', emphasizing a flat, sandy or gravelly shore, while 涂 means 'mud' or 'silt', highlighting the soft, wet, nutrient-rich substrate. Together, they describe a dynamic ecotone where marine and terrestrial environments meet.

Tidal mudflats are ecologically vital: they support rich biodiversity, especially migratory shorebirds, crabs, shellfish, and juvenile fish. In China, major滩涂 areas include the Yellow Sea coast and the Yangtze River Delta. They’re often protected as wetland reserves or used for aquaculture (e.g., clam farming), though reclamation for development poses conservation challenges. The term is formal and scientific but also appears in environmental news and geography education.