Water symbolizes your subconscious, your emotions, and your accumulated life experiences, and the flow of 'feeling' energy. It is also a symbol of new life, refreshment, vigor, energy, cleansing, emotional stirrings, fertility, growth, and creative potential.

Dogs represent love, loyalty, devotion, obedience, intuition, generosity, protection, and fidelity. May also suggest a skill that you have ignored or forgotten, but needs to be activated.
Alternatively, consider the notions associated with the word dog, such as loyalty ("man's best friend") and to be "treated like a dog", or something/someone in your life is proving to be a "dog" meaning, less than desirable.

Black is symbolic of secrets, hidden things, and the unknown or the unseen. It's also a masculine color.

The number 3 symbolizes the trinity. It is an active or a process number (something is going on in the psyche). The number three may symbolize vision(forward thinking), completeness, and fulfillment. Also, anything that may contribute to your personal fulfillment for example, the resolving of conflict between two opposing forces.
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Are you keeping a secret?
Have you been feeling peaceful about someone or something?
Have you 'come to terms' with a part of yourself or someone else?
Have you recently experienced the love and loyalty of someone close to you?

Hope that helps!
Good luck!

That may very well be. He may be serving as a reminder to not repeat the same mistakes...or possibly guiding you to the one who is right for you! Good luck!