Wim Hof can withstand extremely cold temperatures for long periods of time, and also has a scientifically-tested boosted immune system.  The scientists who tested him said he was an exception, but he countered them by saying he could teach it to others, and that's what he did.  This astounded the scientists, and inspired me to get into winter bathing and take cold showers every day, which has helped me be much healthier now in these Scandinavian winters.