Other forms: undercurrents
An undercurrent is a mood or atmosphere just below the surface, like the undercurrent of anxiety in your school during final exams.
The figurative meaning of undercurrent is more common than its literal definition, "an ocean current that runs beneath the surface of the water." Another word for this kind of undercurrent is a "subsurface current." When most of us use the word undercurrent, however, we're talking about a general state of mind, something that subtly influences the way people feel, like the undercurrent of suspense running through a good horror movie.