Phelps aims to 'let loose' in 200m fly final

There was a new face among the thousands who turned out to see Olympic superstar Michael Phelps at the US Olympic swimming trials on Tuesday -- his baby son, Boomer.

"Boomer was up there tonight, yeah," said Phelps, whose fiancee, Nicole Johnson, brought the little one to the CenturyLink Center. "I'm hoping he was awake for my race."

Phelps won his 200m butterfly semi-final in 1:55.17 to grab the top seed for Wednesday's final ahead of Pace Clark (1:57.27), Tom Shields (1:56.35) and training partner Chase Kalisz (1:56.48).

Although Phelps topped their times by more than a second, he found plenty of flaws.

"It was decent," he said. "I probably would have liked to have been a little faster, but I get to swim in the middle of the pool tomorrow. That's not something that I had a chance to do that much this year."

Phelps, whose 22 Olympic medals include 18 gold, is back from a short-lived retirement in the wake of the London Games, trying to add a final flourish to his remarkable career during the Rio Games in August.

He will celebrate his 31st birthday on Thursday, and seems to be enjoying his role as an elder statesman.

"There have been certain people that come up to me and asked me little questions," he said. "Like this guy asked me today, 'What do you think about before you swim?'

"And I was like 'Nothing! I don't think about anything.'"

"I've told a couple of swimmers, just turn your mind off," Phelps added. "You've done the work to get here, so it's just time to get in the water and let it loose. I think I need to use that advice tomorrow."