Being in the flow state is both hyper-vigilant and totally unresponsive at the same time.
Book: The Rise of Superman: Decoding the Science of Ultimate Human Performance
Scientists describe flow as a "state of consciousness" or an "altered state of consciousness". Though there's no clear taxonomy of different states of consciousness, some researchers divided it by degrees of focus and alertness. The results are a spectrum of attentional categories, from a vegetative coma being "total unresponsiveness" to a fight-or-flight response being "hyper-vigilance".
However, Steven Kotler, the Founder of the Flow Research Collective, argued that the flow states might not exactly fall on this scale. Studying science behind ultimate human performance in extreme sports and decoding the neurobiology of flow, Steven Kotler stated that flow is not like other states of consciousness.
For extreme sports athletes in the flow states, the concentration is nearly total for the task at hand. Laird Hamilton, the big wave surfer, can see every nuance of detail from the giant wave he was riding. Nevertheless, he heard nothing of the screams and cries of warning coming from all the people around. Beyond his goal, his awareness dropped off precipitously. He is both hyper-vigilant and totally unresponsive at the same time. Therefore, unlike most consciousness states that are defined by a singular type of attention, flow breaks boundaries, straddling multiple categories at once.