Michael Phelps is diving right back in to competitive swimming.<br /> <br />He's the world's most decorated Olympian with 18 gold medals.<br /> <br />And though he announced his retirement following the London Olympics, he'll be competing again starting Thursday.<br /> <br />(SOUNDBITE) (English) FORMER OLYMPIC SWIMMER, MICHAEL PHELPS, SAYING:<br /> <br />"I'm signing - not that I know of - any contracts. I'm doing this because I want to."<br /> <br />For starters, he'll be swimming in Arizona's 2014 Arena Grand Prix.<br /> <br />But there's speculation this will lead to an Olympic return for the 2016 games.<br /> <br />(SOUNDBITE) (English) FORMER OLYMPIC SWIMMER, MICHAEL PHELPS, SAYING:<br /> <br />"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."<br /> <br />The 28-year-old Olympic legend admits he had fun during a two year hiatus. So much fun that he gained 30 pounds.<br /> <br />(SOUNDBITE) (English) PHELPS' COACH BOB BOWMAN SAYING:<br /> <br />"Well when he first came back, he was so out
