下沉

下沉	xià chén	to sink down
下	xià	down / downwards / below / lower / later / next (week etc) / second (of two parts) / to decline / to go down / to arrive at (a decision, conclusion etc) / measure word to show the frequency of an action
沉	chén	to submerge / to immerse / to sink / to keep down / to lower / to drop / deep / profound / heavy