At 63 years old, Wim Hof, the Dutch motivational speaker known as the Iceman—for his Guinness World Records–famous feats of cold-related human endurance—has been thinking about warmer pastures, having recently mooted over the purchase of 10 hectares of Australian rain forest on the border of Queensland and New South Wales. “I love the cold,” says Hof. “I don’t like it, I love it. Because it is such a powerful tool. But I’m a sucker for botanical gardens.”

Dressed in a zany floral-print shirt and bright blue, thigh-skimming board shorts, Hof bellows about the benefits of his Wim Hof Method (WHM), a combination of deep-breathing techniques, cold exposure and ice baths. “Your body becomes stronger inside to oppose the stress from the outside,” he says. “That’s why...