The speaker imagines themselves as a lily floating down a stream, moving slowly and carefully, watching the world go by. It's a quiet, almost dreamy picture, but also a lonely one. The speaker admits to being alone and having no purpose, as if drifting is all there is.
Everything changes with a single glance. The speaker sees someone with eyes as blue as the water, and the two look at each other. When the other person smiles, the drifting stops. The speaker comes to rest beside them, suddenly filled with "purpose and dedication like no other."
The mood moves from calm melancholy to warm, hopeful tenderness. The short final line, "Love," names what has happened, almost like a sigh of relief. The water imagery ties it together: the same stream that carried the speaker aimlessly now brings them to someone worth staying beside.