He sat quietly, eyes closed, dozing in the shade on a warm afternoon at a beach hotel patio near Barra Olympic Park.
It had been an exhausting first week at the Rio Games, always in demand for selfies and lots of camera time on the videoboard at the pool.
Yep, Boomer Phelps was wiped out.
The 3-month-old son of the most decorated athlete in Olympic history became a star from the stands at his first games. Even his daddy Michael Phelps needed a second Olympics before he grabbed the world's attention with his gold-medal swimming feats.
All Boomer had to do was gurgle in his mother's arms while wearing cute red, white and blue outfits and tiny noise-canceling headphones.
The world fell in love with the little guy.
"I don't think we realized how much Boomer would become a star," said Nicole Johnson, Phelps' fiance. "It's fun to watch as a mom."
This is Phelps' new role: dad. After winning five golds and a silver in Rio, bringing his career total to 28 medals, including 23 golds, Phelps is relishing the chance to watch his first child grow up.
The kid is already a force on social media. One of Johnson's favorite online spoofs was a Huffington Post article written in the first person with Boomer's imagined thoughts. She removed Boomer's headphones at medal ceremonies almost as if on cue from her son.
"Sometimes he would get fussy," she said. "He'll grab his ear, 'Come on, Mom. I'm done, take these off.'"
Phelps has gotten a kick out of his infant son's effect on people. Boomer has his own Instagram account set up by mom and dad, and it's gained over 500,000 followers since the recent U.S. Olympic trials. Phelps badgers Johnson to supply a steady stream of fresh photos.
"I've got to keep everybody happy," he said, grinning. "It'll be fun to share this experience with him. Hopefully, in four years he'll be able to understand a little bit and I'll get a chance to take him to Tokyo."
Phelps will be at the 2020 Summer Games not to swim but to be himself, making sponsor appearances and promoting the sport that made him the world's most recognizable swimmer.
He was working Tuesday, making an appearance on behalf of Krave jerky, a new endorsement. The hotel chef created eight different entrees using such Krave flavors as chili lime, basil citrus and black cherry barbecue for Phelps, who grabbed lunch with Johnson while former Olympic swimmer and mother of two Summer Sanders expertly rocked Boomer in her arms.
Boomer's navy shirt from his father's MP clothing line and navy-and-white shorts nearly matched his dad's navy shorts and white Team USA jacket. The infant had better kicks, though. Boomer's tiny red, white and blue shoes with gold soles easily outdid Phelps' flip flops.
Phelps can't wait to return home to Arizona and settle into a retirement of changing diapers, bottle-feeding and watching Boomer grow. Johnson said Phelps was able to assume his role as new dad for just three weeks in the run-up to Rio.
She sees Phelps channeling his famous competitive drive into expanding their family and raising their kids.
"I think that's where his drive and focus will go," she said. "He's been awesome with the little amount he's been able to give of himself."
Phelps feels a bit more ambitious, though.
He wants to help empower the world's swimmers when it comes to the sport's decision-making and changing some rules to benefit them.
"There are a lot of things that bother me about the sport and how they're handled," he said, specifically citing Rule 40 of the Olympic Charter.
It prevents athletes from using their name, picture or performances for advertising while competing in the games, and keeps them from touting their sponsors on social media.
"If I need a pair of this brand's shoes or shorts or T-shirt or X, Y Z that are going to help me perform and I can't wear them because of Rule 40, it stinks," he told The Associated Press. "Those things I think we should be able to do. Without the athletes, it doesn't happen. We want to make sure the conditions are perfect for us."
Phelps wants to continue promoting water safety for youngsters, including his own son.
Johnson has been planning the couple's destination wedding to take place near the end of the year. It'll be a small affair followed by a big party most likely in Arizona.
"We'll see where Boomer decides it needs to be," Johnson said. "We're on Boomer time."