Submergent coastlines or drowned coastlines are stretches along the coast that have been inundated by the sea by a relative rise in sea levels from either isostacy or eustacy.
Submergent coastline are the opposite of emergent coastlines, which have experienced a relative fall in sea levels.
Many submergent coastlines were formed by the end of the Last Glacial Period (LGP), when glacial retreat caused both global sea level rise and also localised changes to land height.
Features of a submergent coastline include rias, which are drowned river valleys and estuaries, and fjords, which are drowned glaciated valleys.
Notable and illustrative examples of submergent coastlines include: