Michael Phelps, 28, has fuelled speculation that he could he could compete at the 2016 Rio De Janeiro Olympics.
The record Olympic medal holder will jump in the pool next week at a meeting in Arizona, for the first time since the 2012 London Games.
The news has shocked the sporting world after Phelps said in 2012 that he didn't want to swim once he was in his 30s.
Speaking back then, Phelps said: "I don't want to swim after I turn 30 and that is in three years and I don't want to swim for another three years.
"I would be past 30 by the time the next Olympics. I have achieved what I wanted to achieve, Bob (coach Bob Bowman) and I have somehow been able to do every single thing.
"If you can say that about your career then it's time to move forward, time to move on to other things. I finished my career how I wanted to."
Long-term coach of Phelps, Bob Bowman has played down the swimmer's return, saying it may not be the comeback it is being billed up to be.
He said: "I think he's just going to test the waters a little bit and see how it goes.
"I wouldn't say it's a full-fledged comeback."
Bowman also went on to say it was refreshing to see Phelps to be swimming out of enjoyment.
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