The term 'plumbs the depths' is an idiom that means to explore something thoroughly. It is often used to describe a person who is trying to understand a complex topic or situation. The crossword solution for this term is 'SOUNDS', which can be interpreted as someone listening carefully in order to gain a better understanding of the subject. Therefore, the phrase 'plumbs the depths' can be interpreted as someone who is taking the time to explore a topic or situation in great detail.