Hooray for daddy! Michael Phelps made history on Wednesday, June 29, when he became the first U.S. male swimmer to qualify for five Olympics — and his son Boomer was his biggest cheerleader.

The 18-time gold medalist, 31, made the cut after swimming the 200-meter butterfly in Omaha, Nebraska. Phelps didn't have to look at the scoreboard to know what he achieved, either. He touched the wall and immediately raised up five of his fingers to the audience before the times were officially announced.

"With everything that's happened and being able to come back, that was probably harder than any swim I've had in my life," Phelps said after the race, via ESPN. (Phelps retired in 2012 following the London Games, but announced his return in April 2014.)

Phelps was cheered on by his fiancée, Nicole Johnson, and their newborn son, Boomer, in the crowd. The couple welcomed their first child together in May.

"Congrats Giggles on making the Rio Olympic team and thank you auntie @arschmitty for making @boomerrphelps smile #weloveyou," Johnson, 30, captioned an Instagram photo of Boomer on Wednesday night. The bride-to-be continued to celebrate on Thursday, which just so happened to be Phelps' 31st birthday.

🎉Congrats Giggles on making the Rio Olympic team and thank you auntie @arschmitty for making @boomerrphelps smile #weloveyou

A photo posted by Nicole Michele Johnson (@nicole.m.johnson) on

"HAPPY BIRTHDAY to my incredible fiance and the BEST daddy @boomerrphelps could ever ask for!!" she captioned a pic of Phelps and their baby boy. "31 is going to be a "record year" for sure!! Your past has written history, your present is writing history, and your future is about to make history! I love you @m_phelps00."

Phelps' latest swimming trial is meaningful in more ways than one. As previously reported, the 6-foot-4 star (who has 22 Olympic medals in total) checked himself into rehab in 2014 following two DUI arrests.

"It’s pretty crazy how big of a change I see from not having a drink … I see a complete change in how I am day to day. [I’m] completely clear-headed," Phelps told the Today show's Matt Lauer in April. "I’m actually happy every day. I’m actually able to be productive every day. I think that’s something that I am very proud of and, you know, I think when I do retire I’ll be able to look back and say that [rehab] was something that really helped."

The Rio Olympics begin August 5 and will be streamed live on NBCOlympics.com and the NBC Sports app. The Rio Paralympics begin on September 7 and will be streamed live on TeamUSA.org.

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