Though I wonder that someone out there has proposed this hypothesis, I would like to use my own reasoning to give a shot. So it starts with my dream at noon as usual. I, like always, controlled myself to maintain at a state which my eyes could open and notice things around me, telling myself that I am in dreams, while allowing my brain to maintain heaviness and drowsiness. Simultaneously, my imagination flew without too much of a control---I only need to think of what the story line could go towards: (in dream) I hug this person, (then the dream tells me that this person is my dad). I ask him why he is here (he told me he is here for picking me up for home). (Consciously I want the story to be more exciting, so I direct myself to leave my dad). Then I tentatively picture some random person(an unfamiliar face/location can spontaneously pop out). Sometimes I can direct the stories to go too fast and so my dream flows in a direction, like I am in class and I am talking to a person next to me (I thought “I want him to hold my hand” repeatedly) but the dream just goes like “class, leave the class, pond, home” or other random stories. Initially, I guess that dreaming this fast (happened 5-20 min), which is REM state without other entrance, is a good distraction from the reality. Dreaming released my tension from thinking things in real life. Yet another thought comes into my mind. If when we are super tired, we can go into REM very fast, which allows us to forget troubles that poisons us throughout a long period of awareness, and rapidly restore a new mind when wake up. In this REM, however, we can dream while be “floating” on a shallow surface: we are aware of our surroundings, and float between real awaken and lose of awareness. This could be a very efficient way to be alert of danger while resting our body and brain. Just like hunter-gathers, if they are super tired of chasing the preys for days and nights, while afraid of being preyed and killed when they are sleeping, both alertness and sleepiness and work at the same time. However, what neurons, and what neurotransmitters are in charge of these behavior? How could we prove that, assuming two specific groups of neurons are doing awareness and unawareness, can work at the same time? What if, that cetaceans are doing what I am doing, sleeping while being alert?