Where a river meets the sea, fresh and salt water mix, so the estuary is read as a transition between one stage of life and a wider one. Dream books link it to letting something personal open into something larger.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.