Whether humans possess a latent animalesque capability of metabolic downregulation, to subBMR-low, time-dilated-slow & anapyrexia-cool levels, ideally, fast like diving seals & sustainably like hibernating bears remains an open question & centuries-elusive, say, holy-grail, physiological & biomedical grand-challenge. Cracking the metabolic enigma code of this dark region of the metabolic spectrum would profoundly enlarge the scope of metabolic protection & survival in extreme & austere environments, e.g., asphyxia, hypoxia, hypo/hyperthermia, hypo/hyperphagia, hypoydration, infection, hyper/hypogravity, hypokinesia, IR radiation, scar-less wound-healing, neuro-remodeling, fast-track & cross-transplant acclimatization, biological time dilation, etc., etc., i.e., motherlode platform of biomedical superpowers. There exists a notion that various animal bradymetabolic states are somehow connected & may be enabled via a universal “master switch”,[1] e.g., diving seals & hibernating bears basically express the same physiological features.[2] Certainly, it sounds logical, neat & efficient, & would make ID this dimmer-switch easier. The idea of isolating the switch & trigger by turning to human divers[3] makes much sense since one might expect that any humans capability, if it exists, would most likely on-demand express in the face of the “heroic measures to the threat of asphyxia,”[1,3] & with that animalesque-classic & quintessential-telltale hallmark, spontaneous brain cooling. Presented here, glimpse outcomes of investigations of human brain cooling phenomena involving dozens of trials & spanning several years undertaken time ago on a human diver (the author) as part of a long-running R&D program exploring such exotic states for various enhancement apps. Specifically presented, best-in-class outcomes & mechanistic insights behind all-natural, prompt, ultra-rapid & profound super-cooling phenomena expressible from normothermia.[4] Essentially, basically, the mechanism involves animal diver & hibernator strategies, also employed by the author for deep diving, namely, long expiratory pauses between breaths.[5] The mechanism allows brain-wise preferential redistribution of cooled blood from thermal windows for protection against a relative hyperthermia under the threat of hypoxia. Notable, due to a greater relative metabolic demand & hypoxia sensitivity, brain cooling expresses faster than in a seal, as evidenced by the less pronounced GI-tract cooling (Fig.2): 0.4±0.1°C (mean±s.d., n=5; e-Celsius, BodyCap, ±0.2°C). Supporting data suggests the limit in diving may be on par with that of a similarly sized seal or bear, ∼32°C.