Water, to me, has to do with pure self. It is the elemental self, aside from the burning energies of yourself or anyone. It is neither good nor bad, but simply is.
If symbolism is what you're looking for, it seems to me that you anticipate some event that will "overwhelm." Yet, to me, it can't actually occur. If you take for example the silly film "2012", it represents an "overwhelming" that leads to the destruction of people and places. Symbolically, however (and according to most who have actually studied Mayan philosophies and religion), this 2012 event simply represents the end of their calendar and the promise of yet another new "beginning." It is both an end AND beginning. It is an awakening. How optimistic that is! What a wondrous thing! And our pure selves, as constantly being extended from the source itself, cannot be overwhelmed or extinguished. The essence of what we are always has been and always will be.
Accept the dream as a mark of coming "change"-- that's all. If you must anticipate, anticipate a purification-- not simple destruction. And I believe the "water" is you, augmented by unfocused imagination and generated by anticipation. If you picture that dream again, turn the volume down in your mind, breathe and embrace the wave with pure, warm light-- you'll see the sun come out on the other side in no time, just as after any "storm." Let the "wave" wash away the anticipation, the fear it can generate-- put your hand to your heart, breathe the warm air deeply and laugh away the joke that it was playing on your psyche. It was you all along-- appreciate the imagination, humor and creativity in that; and move on. Celebrate a renewed self! It'll be wonderful not having all that "debris" anymore.