Ibn Sirin
Falling in Deep Waters — Islamic interpretation
From Imam Muhammad Ibn Seerin's Dictionary of Dreams According to Islamic Inner Traditions — entry "falling in deep waters" (page 151).
Falling into deep waters and not reaching the bottom of it in a dream means prosperity and wealth, for the world is a deep ocean. A sudden fall into water in a dream also means joy and money.
Note: Islamic dream interpretation depends on the dreamer's circumstances and state. This is a general guide drawn directly from the source book.
These interpretations are reflective and cultural — not predictions, and not medical, psychological, financial, or other professional advice.