Dreams about Black water ( Dark Water ) tend to offer clues to your emotional state.Where the water is black, and you are afraid of it, or fall into it, or can't see, yet the water is calm on the surface, this imagery conveys an impression that you present yourself to the world as "still waters run deep", someone who is outwardly calm on the surface, but inside is another matter, with all manner of powerful emotions going on.
The Land of Black Water
The condition of the water indicates what your emotional state is at the time of the dream. Black Feel- That you are afraid of what is going on under the surface, or can't see what is going on under the surface, suggests that you don't want to get too deep into exploring your own emotions, they are powerful, and you are afraid of them, and perhaps afraid of what others would think if they knew how you really feel about stuff.
The second image conveys this sort of idea as well, here we have other people navigating emotional territory (they are swimming in the water) yet there are sharks in it, and you wonder how others can deal with their emotions when you feel you can't, you feel like you could be over powered by your emotions.
The Black Water Powers Black Feel
Your emotions are so strong that you don't even want to know what you really feel about stuff. The one about falling in to the water suggests a fear of being "drowned", in this context, a sense of being emotionally over whelmed.