She submerged the vegetables completely in water to wash them.

submerged 是动词 submerge 的过去式。submerge 由前缀 sub-（表示"在...下面"）和词根 merge（"浸入、合并"）组成，字面意思是"浸入下方"，即"完全浸入、淹没"的意思。