The phrase "beneath the surface" refers to something that is hidden or concealed. There are several synonyms for this phrase, including "hidden," "underlying," "latent," "concealed," "submerged," and "unseen." These words describe something that is not immediately apparent and may require further investigation or analysis to uncover. "Subterranean" and "underground" are also words that can be used to describe something that is hidden or beneath the surface. These synonyms can be used interchangeably, depending on the context and intended meaning. Whether you are talking about emotions, ideas, or physical objects, using synonyms for "beneath the surface" can add depth and complexity to your writing.