On the blocks, at his best, he wore a swimsuit, goggles, a cap and one more thing you couldn't see. A second, invisible skin. An armour which he had built through time.
Faith in the work he'd done. Trust in the skill he had.
Or, as Joseph Schooling, whose half-smile is always lurking, said last week: "It's believing you can do anything you set your mind to." Like going from Bedok Reservoir Road to the top of an Olympic podium.
So, what's it like to have this belief, do you feel almost invulnerable?
"Absolutely," he said. "It feels like everything you touch turns into gold. It's a combination of feeling confident and relaxed at the same time and believing that you can do no wrong and you will do no wrong whatever the cost."
It's not just him, it's all champions, who carry self-assurance like a muscular calling card. You can even see this belief in the old Tiger Woods stare, in Rafael Nadal's retrieving, in LeBron James' body language. As every coach says, it's all in the mind, kid.
But belief never stays, for defeat dilutes its strength and indifferent form makes the certain athlete question himself. Schooling has been to both places, he's owned belief and lost a little, but the search for it is what comprises the athletic life.
Belief is hard to explain because it's a feeling, a knowledge, a sense of yourself. It's what Schooling had in 2016 in Rio when he won, but it's partly what he feels he always had.
World Championship, 2017
• 100m butterfly, Bronze
Olympic Games, 2016
• 100m butterfly, Gold
Asian Games, 2014
• 100m butterfly, Gold
"I think you're born with the mentality. You can't teach people to get up in a race, you can't teach people how to switch on, but you can prepare for it as best as you can."
Schooling is clearly competitive, but belief has to be polished with victories and manufactured in practice. It's built by work ethic or, as the runner Haile Gebrselassie said: "First, do enough training. Then, believe in yourself and say, I can do it."
Schooling slogged and this is the part of him we never saw, all those monotonous kilometres, all that liquid concentration, all that willing of yourself to beat a teammate in the next lane even on bad days, all that pushing through pain till you tell yourself nothing can stop you.
"The most self-belief I've ever got," he explains "is after an accumulation of practice sessions where they're really tough and the coach tries to break you and throws everything he has at you and it's almost like you break through a barrier. That's when you build up the most confidence."
But if practice fuels his belief, so does one race, in June 2016, before Rio. Michael Phelps, that laconic aquaman, comes to Texas for a warm-up race and Schooling is exhausted and still wins and it's like an intravenous injection of belief.
The most self-belief I've ever got is after an accumulation of practice sessions where they're really tough and the coach tries to break you and throws everything he has at you and it's almost like you break through a barrier.
"I was so dead from practice, I felt like I had nothing, (but) I just wanted to race. Everyone wants to beat Michael, he's the best. But I knew that if I could beat Michael the way I was feeling now, I had a legitimate shot at doing well in Rio. And after I won, the time wasn't good, but it was the fact that I set myself up mentally to do well in Rio and I think that was the final turning point."
After victory in Rio, Schooling's dip was almost foreseeable. A young man invests an entire austere life in a single moment and then, 50.39 seconds later, it is done. The world is beaten, the dream done, the anthem played. At 21.
Now what, athletes wonder. And from his Olympic peak, Schooling had to descend to normality for a while, untie the bonds of discipline, loosen the knots of ambition, eat too much nasi lemak, put on more than 6kg at one point last year, lose at the National Collegiate Athletic Association (NCAA) meet and slip back to bronze at last year's world championships.
The scoreboard tells unblinking truths and Schooling is honest and he will tell you his belief took a hit last year. "Yaah, definitely. I trained hard the second part. I thought I did enough to get by in the summer, but it wasn't." After this year's NCAA, he told himself: "All right, I'm done sucking, enough is enough."
But this post-Olympics journey is a necessary ride, an education, a chance to reassess his life and gauge his motivation and reset his ambition. Now, in Singapore, he's looking different - a little leaner, a little older, a little clearer in his head.
Belief is being built again, length by length, and it's hard, for improvement is never a guarantee. He hasn't gone faster in the 100m butterfly since Rio, but every athlete has been here, to this place where sacrifice brings no reward, when you plateau despite practice, when the clock doesn't recognise your effort. But frustration has to be met with faith.
Schooling knows this, but sometimes when legends say it, it has a more reassuring weight. "I asked (Michael)... has there ever been a time when you're just like, I'm done with this or you feel like you're not getting better, and he said there was a span of three, four years when he didn't get a best time and it was really frustrating.
"Obviously, you get killed in the pool and you put in everything and obviously, you want something to come out of it, but all Michael said was, trust the process, listen to your coach, stay positive. And that really stood out for me."
It's nice to see Schooling back home, at ease with strangers, making speeches at lunches, wearing his new corporate cloak with an adult charm. Champions can have an effortlessness about them, but they also undergo great internal struggle.
One of the hardest things in sport is to wear a crown, to understand what you've accomplished, to handle the expectation, to appreciate that one journey is over and another awaits, to know that you were one swimmer then, but must be another one now. He can't go back to who he was, only forward.
Nothing is the same. His training is different, his mentality different, his status different, his rivals different. He's still chasing medals, but in a different body and down a different route. He can't be the swimmer he was in Rio, he has to be a faster one. As he wisely said: "I don't think anyone ever really feels the same as he once did whenever you've done amazing things. And you can't ever do the same things if you want to get better."
So he'll push, he'll drive harder, because embracing challenge is his way of living more. If once he chased Phelps, now he hunts Caeleb Dressel and when I ask, 'Is he the guy you want to catch', he replies: "I think he's everyone's guy, that everyone wants to catch. I believe I can, but we'll see about that." Talk is cheap, he knows, proof is better.
Chapters end in sport and new adventures commence. His name is in the history books, but put those away. His parents have his gold medal, but he can't remember when he last looked at it. The boy Schooling is gone, the man has come.
His Games right now aren't Olympic but Asian. His goal right now isn't Tokyo 2020 but Jakarta in August. When he stands on the blocks, Rio won't matter. The clock is back at zero and the only thing he wants is to write a new story.
You better believe it.