A mudflat is what the tide reveals when it goes out, so dream books link it to things exposed in a quiet moment. It stands for low energy, and for what becomes visible when emotion recedes.
Where in your waking life have you met something like this lately?
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.