Dreams involving water, especially deep lakes, often symbolize emotions and the unconscious mind. The fog in your dream suggests uncertainty or confusion about your feelings, while the deepness of the lake may represent the depth of your emotions or unresolved issues from your past.

Your ex-girlfriend's presence indicates that this dream may be related to your past relationship. The wooden boat and lantern might symbolize a journey or transition, possibly reflecting how you or your ex are navigating through life. The fact that she did not respond when you called her could signify feelings of disconnection or unresolved feelings about the relationship.

Feeling both peace and sadness suggests a complex emotional state. You may be coming to terms with the end of the relationship, acknowledging the good times while also grappling with the loneliness and loss that followed.

This dream could be encouraging you to explore your feelings about this past relationship more deeply. Consider what aspects of this experience you need to let go of, and what you can learn from it as you move forward. It may also be helpful to reflect on how these emotions are impacting your current life and relationships.