It's about what Identity means. How do we define ourselves? What labels do we attach to ourselves that make us who we are? Am I a river? If I'm a river, how can I be an ocean? I've always been a river. I know these banks, those rocks, these fish. What lies ahead is unfamiliar, and I'm afraid.
If we can separate ourselves from our perceived identity, we can become closer to a feeling of belonging to this unknown, of being a part of a whole, of being connected to the great Mystery. The river surrenders who she thinks she is and becomes unified with All.