For Sugar Ray Robinson, Joe Bugner, George Foreman and Muhammad Ali, read Janet Evans, Ian Thorpe and Michael Phelps.

If my childhood was punctuated by pugilists on the comeback trail, this role now seems to have been usurped unexpectedly, at least to me, by denizens of the 50-metre swimming-pool.

When the Baltimore Bullet returned to competitive swimming at the Arena Grand Prix in Mesa, Arizona last month, finishing second to Ryan Lochte in his first final since retiring, I decided that a trend had been established.

This was an athlete, after all, who had provided one of the most jaw-droppingly memorable 25 seconds or so of sporting action it has been my privilege to witness, powering back from fifth at the turn to claim his fifth gold medal of the Athens 2004 Olympics in the 100m butterfly.

And I am not even much of a swimming fan.

While I was not sure that I had a great deal to contribute on the subject of why some of the world's greatest swimmers had sought toreturn to competition, I was pretty sure I knew someone who would: step forward Duncan Goodhew, Great Britain gold medallist in the 100m breaststroke at the 1980 Olympic Games in Moscow - and a man who had written a number of penetrating and insightful pieces about swimming and swimmers for the Financial Times sports pages in years gone by.

Goodhew's first response was to say, in effect, that there is nothing new under the sun: Mark Spitz, another of the very top swimmers of all time, winner of that astonishing haul of seven gold medals at the Munich Olympics of 1972, had attempted a comeback 20 years later; and there have no doubt been others.

Michael Phelps made his comeback last month at the Arena Grand Prix in Mesa, Arizona ©Getty Images

The Briton also pointed up a similarity between the amount of work top swimmers and top boxers need to do, referring to the adage, "the more you put in, the more you get out".

His main line of thinking, though, focused on two characteristics of swimming that could, or so one might construe, make it particularly taxing to quit competitive swimming when the time came.

And this bearing in mind that, as he put it, "For any top athlete, retirement is brutal".

For one thing, he argues, swimming is a particularly "objective" sport.

"You know how many strokes you swim per length.

"You know the times.

"You know exactly when you are making progress, and not.

"So it's probably one of the most objective sports you can take part in.

"The training is all comparable to what you have done before."

This transparency, Goodhew explains, can easily feed through into the swimmer's state of mind.

"You get a real high as you do your workouts," he says.

"Breakfast can be a weigh-ho experience because you had a good workout.

"You can tell people who had a bad workout because they are having a bad breakfast."

Duncan Goodhew believes many swimmers return to action becauser "retirement is brutal" ©Getty Images

The other characteristic of swimming that might be germane to us here is that, as Goodhew puts it, it is "very environmental.

"You spend four hours a day actually submerged in the water, in this completely different environment."

The former breaststroker was seeking to highlight both the beauty of this situation - phenomena like sunshine dancing on the bottom of the pool – and its cocooning quality.

"You feel you are in a different world," he concludes.

By the end of his explanation, I am left with a sense of how training could become almost a mystical experience.

So: routine, discipline, transparency and a world apart in which you frequently feel relaxed, empowered and happy.

When you see it like that - and you set it against retirement, where, in Goodhew's phrase, "one day you have complete order and focus and direction in your life; the next you don't have it" - and it starts to appear surprising that all swimmers don't attempt comebacks.

Goodhew repeatedly emphasises that he has no particular knowledge of the situations faced by the names cropping up in our conversation, and I certainly don't, but it seems reasonable to conclude that, even in the case of a swimmer as well-known and talented as Phelps, money is probably well down the list of motivating factors.

"Swimming is not a well-paid sport," Goodhew says matter-of-factly.

In this characteristic, at least, boxing can be very different.

Time is, of course, the enemy of any athlete on the comeback trail.

But it can be particularly so, it seems, in the case of male swimmers, whose upper body strength, according to Goodhew, may deteriorate once they give up "quickly and pretty finally".

The other side of the coin is that, unlike I would argue some other sports, swimming is an activity that former competitors continue to enjoy long after their last competitive race.

"Some swimmers, you slice them any which way and water will come out," Goodhew says.

"It's seeped into the soul almost.

"I judge my day: a good day is a one-swim day; a great day is a two-swim day."

To make a weak attempt at gift-shop-mug humour: old swimmers never die, it seems; they just keep on crawling.

David Owen worked for 20 years for the Financial Times in the United States, Canada, France and the UK. He ended his FT career as sports editor after the 2006 World Cup and is now freelancing, including covering the 2008 Beijing Olympics, the 2010 World Cup and London 2012. Owen's Twitter feed can be accessed here.