It seems like a representation of what you have and are passing through psychically.

There's fear of being overwhelmed (drowned) by stuff coming up from your unconscious - especially after the intensity of emotion after a breakup.

The creek represents the boundary between you and the place of your fears. I wonder if your phone represents the connection to your ex, your mother (nurturer) being concerned and tells you just to leave it when it falls into the creek. Your desire to hang onto that connection causes you to fall into your fears. (Deer are ambiguous as an image of fear. Yes they are wild, but there is a soft side to them.) Nevertheless you are able to experience your fears and they are not what you expected. Rather, what you feared most does not kill you but saves you perhaps speaks to the fear of breaking up.

Quite a broad brush - there!