The greatest Olympian of all time is going after some of his international competition out of the pool, moths after hanging up his Speedo following a successful showing at the Rio Games.
Michael Phelps testified in front of Congress on Tuesday about the need for more drug testing and stricter anti-doping rules, stating that if they did not happen soon many in sports like his would become 'disillusioned' and want to quit.
He then took things a step further by making the shocking claim that every time he competed in an international competition he did not know or think the other swimmers were clean, assuming some had been doping to achieve their results.
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Dope hearing: Michael Phelps testified in front of Congress on Tuesday (above) in Washington DC
Greatest: The Olympic great told lawmakers that if stricter drug testing and anti-doping laws were not soon put in place athletes would become 'disillusioned' (above in Rio)
'I don't believe that I've stood up at international competitions and the rest of the field has been clean,' said Phelps, who spent most of his time at the hearing looking down and reading from his prepared remarks.
'I don't believe that. I don't think I've ever felt that. I know that when I do stand up in the U.S., I know we're all clean because we're going through the same thing. Internationally I think there has to be something done, and it has to be done now.'
Phelps, 31, has had his own history with problematic substance usage, having been photographed with a marijuana pipe in early 2009 and twice arrested for drunk driving.
Neither of those substances did anything to help his abilities however, and the swimmer eventually went to rehab ahead of the 2016 Summer Games.
He also revealed that he was tested 13 times prior to Rio, and often during unannounced visits.
Phelps was not complaining however, but asking why if he had to undergo so much testing, 1,913 athletes in 10 'high-risk' sports were never even tested once.
In total, 4,125 athletes actually had no record of testing in 2016 before Rio.
'For us, sometimes it's annoying when we get woken up at 6 o'clock in the morning but, you know what, I'll do that to make sure that we're all competing at a fair level,' said Phelps.
'I don't believe that I've stood up at international competitions and the rest of the field has been clean,' said Phelps
'I wish I could say that about everybody else in the world.'
Phelps announced his retirement shortly after the Rio Games in an interview on Today.
'Done, done, done - and this time I mean it,' Phelps told host