"Swim upstream" is an idiom that refers to the act of going against the current or resisting the prevailing trend or opinion. There are various synonyms that can be used to convey the same meaning, such as "go against the grain," "buck the trend," "swim against the tide," "defy convention," "challenge the norm," "break with tradition," and "march to the beat of a different drum." All these expressions suggest a willingness to stand out from the crowd, to follow one's own path, and to question the status quo. However, it is important to note that swimming upstream can be both exhausting and rewarding, depending on the context and the outcome.