Michael Phelps has left the water. It's like Yo-Yo Ma putting his cello down forever. It's inevitable as it is affecting. It will be said, as a sort of precise epitaph, that Phelps, 31, won 28 medals at five Olympics but the greatest number in his life is an inexact one: It is the numbers of us he brought to swimming. He led us to water and he also made us watch.

We have loved swimmers before, some of us from as far back as Johnny Weissmuller, the five-time gold medallist from the 1920s who our fathers introduced to us as Tarzan in the movies. Weissmuller fought crocodiles, Phelps just manhandled men and clocks. For a long while, time bent to his skill.

Phelps was unique because he was a self-confessed salesman. Water was his product. To get you to watch people in it, he had to rule it. "I wanted to change the sport of swimming," he said the other day and on many days. He wanted to make it like other sports, not just a four-year Olympic oddity but an annual spectacle. After Beijing 2008 he told this writer: "You can't doubt. If you doubt, then that's it." He was talking about his racing but meant the same about his mission.

Almost single-handedly Phelps fought against our ingrained biases. Fastest Man In The World for us was instinctively a creature of land. And he happened to be a Jamaican with style and a smile. You could see Usain Bolt, but Phelps was hidden under goggles, two caps and a sheath of water. But he was so fast that once he peeked at the scoreboard as he swam.

Every time Phelps won he understood that he was not merely collecting a medal but making a pitch for his sport. He did it so well that he turned his winning of medals into an amusing game in itself and every four years we asked: If Michael Was A Nation Where Would He Stand?

With 23 medals of that colour he became the gold standard. On Saturday, his last night, a woman athlete who has a bronze from a previous Games and is deeply proud of it, laughed and told me: "We only tend to count his golds. It's like for Michael the bronzes and silvers don't even matter."

Phelps' ability to win taught us a lot. Even about wildlife and mythical monsters. We opened books and looked up seals, sharks and leviathans only to draw analogies with him. But it wasn't enough to win; to attract extraordinary attention the athlete must embrace the extraordinary. A feat of such weight, of such versatility, endurance, technique and luck that it was almost mythical.

It came with his eight golds in 2008. He won one race by .01 and another, a relay, by .08 from France. A Frenchman had earlier said his team would smash the Americans but when he, defeated, floated in the pool, it was Phelps who leaned down to shake his hand.

Beijing was a masterpiece in winning and a reminder of what Ian Thorpe said to this paper in 2008: "You train for feeling dreadful and producing a good swim and you train for swimming perfectly and not having a great day." Phelps had worked till he was ready for anything and provided us with a one-time gift. In the next 25 years of my life I might again see five Wimbledons won in a row and four golf Majors won in a year. But eight swimming golds in a single Games? Never.

People still believe Phelps will return: Not so much because he finds himself when dipped in water but because he loses himself sometimes on land. There has been the drink-diving, the depression, the rehab and like so many great athletes the quiet nothingness of retirement that is hard to negotiate. And so they return to sport and its routine, its purpose, its adulation.

Phelps deserves the contented retired life, for anything less would be unfair. He started swimming as a boy and now he has one himself. He has done enough. He has made kids dream of being him and beating him, he has made crowds come, he has earned a rare respect. In Rio, men he had defeated were asking him to reconsider retirement.

On Saturday night I went to the pool out of inquisitiveness but also respect. In the 4x100m medley relay he won gold. Of course. When he dived in America was second and when he finished his leg America was first. Of course. I was standing behind a cameraman later and among the 32 swimmers on deck, he was focused only on Phelps. The American was bent over, arms on knees, as if spent of energy and emotion. Everything given to swimming. Everything.

My last sight of him was a familiar one. Seen by us in Athens, Beijing, London, Rio. He held his flag, he bit a gold medal, a flash went off. This was Phelps' world. Behind him the water was still. Now it is someone else's canvas.