The ferryman is an old figure of crossing between one shore and another. Dream books read him as a passage from one phase of life to the next, rather than anything literal.
When this appeared in your dream, what were you feeling?
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.