Dreams involving water often symbolize emotions and the subconscious mind. In your dream, the presence of a random guy swimming in dirty, brown polluted city water could reflect feelings of being overwhelmed or affected by negative influences in your life. The polluted water might represent toxic situations or emotions that you or someone in your life is navigating.

Seeing someone else in this scenario might suggest feelings of helplessness or concern for others who are struggling. It could also indicate a part of yourself that feels trapped in difficult circumstances.

To gain more clarity, consider the following questions:

• How did you feel while watching this person swim?
• Do you relate to this person in any way, or do they represent someone else in your life?
• Are there any current situations or relationships that feel 'polluted' or unhealthy to you?

Reflecting on these aspects may help you understand the underlying emotions or situations that your dream is trying to bring to your attention.