Final answer:
An 'undercurrent' can also be referred to as a 'subcurrent', which represents movement or existence below the surface, comparable to submarines that navigate underwater and conductors guiding trains.
Step-by-step explanation:
“Undercurrent” can also be referred to as a subcurrent. This term captures the essence of something that moves or exists below the surface level. Just as SUBmarines move under water, and a conDUCTOR is responsible for making a train move, an undercurrent or subcurrent suggests movement below the superficial layers. This concept can be extended metaphorically, perhaps in literature or conversation, to suggest an underlying feeling or opinion that is not immediately obvious or visible, much like an undercurrent in the sea that affects the movement of water without being immediately apparent on the surface. This underlying layer can greatly influence events or behaviors, much like the subtle movements in the excerpts we've seen, where undercurrents or similar forces play a role in the narrative or depiction of a scene.