TODAY | April 24, 2014
>>> michael phelps , most decorated olympian of all time, makes his return to the pool today. the 22-time medal winner will compete in mesa, arizona, his first competitive race since the 2012 london olympics . janet shamlian is there. good morning.
>> reporter: he is calling himself the grandfather of today's games and downplaying expectations of how well he'll do. that is a tough sell for michael phelps . after all, this is a guy who has 18 gold medals . it's been almost two years since he famously hung up his goggles after london, but as of today, phelps is officially back. testing the waters. retired swimmer michael phelps , the most decorated olympian ever, 22 medals is as of today now unretired i just miss being back in the water.
>> reporter: phelps said he was finished two years ago after a spectacular finish in london.
>> michael phelps is going to win gold!
>> reporter: but like basketball's michael jordan and football's brett favre , swimming superstar has decided to lay it on the line and go for the hollywood style ending, a return to greatness.
>> michael has never been, is not now, never was, never will be afraid to fail. he's like, let's bring it on now.
>> reporter: the first stop is here in arizona, where phelps , who warmed up wednesday, will race in a few hours, after what he describes as an almost two-year vacation.
>> i traveled. i played golf. i gained 30 pounds.
>> reporter: his long-time rival will once again race against phelps .
>> there is no doubt in my mind he'll put fast times up there. we'll see how it goes.
>> reporter: is this a run for real?
>> i guess i'm at least going with my mom whether i'm in the pool or in the stands. i guess time will tell.
>> reporter: nothing would make his number one fan happier. mom debby phelps always in the olympic audience said in 2012 she is not ready for her son to say good-bye.
>> it becomes part of your culture and part of your family.
>> no one has won more!
>> reporter: as the superstar looks to join the ranks of the comeback kids. his race today is the 100-meter butterfly. he is the three-time defending olympic champion in that event so what would it be like to be one of the young upstarts today in the next lane? knowing you've got phelps racing against you.
>> might be taking some self-ies in the pool. janet, congratulations to michael phelps , grandpa, back in the pool.
>> we wish him luck. glad to see him back in the sport.