Parents and children have been staying up way past their bedtimes to watch the live broadcasts of his races. Working professionals who don't normally obsess over swimming have found themselves ducking away from their desks to catch even the preliminary heats during the day. And swim clubs and swimsuit retailers across the area say their pools and shops are abuzz with talk of Michael Phelps and his history-making performance this week in Beijing.
"Oh my gosh, I've been up until 12:30 in the morning almost every night," said Katie Berman, a 27-year-old elementary school teacher who lives in Canton. After a concert at the Inner Harbor one night, she and six friends even dashed into a nearby hotel bar to watch one of Phelps' races before speeding home to catch the next one.
As Phelps has torn through the record books in China, piling up more gold medals than any Olympian in history and challenging the decades-old record for the most golds in a single Olympiad, the former Rodgers Forge resident has sent waves of excitement for his sport rippling across the region.
In 2004, when Phelps hauled in six gold and two bronze medals in Athens, dozens of swimmers, fans and families affiliated with his swim team gathered for nightly watch parties, and thousands of people turned out for a parade in Towson to welcome him home.
But this year, with NBC setting its Olympic broadcast schedule around his prime-time races, the swimmer - and his sport - have gained an even higher profile.
"It's been a long time since a swimmer has been a poster child of the Olympics like this," said John Cadigan, general manager of Meadowbrook Aquatic and Fitness Center, the Mount Washington pool where Phelps and fellow Olympian Katie Hoff have trained.
"It really raises the level of awareness about swimming, both for the casual lap swimmer and for kids interested in learning to swim, but it also increases interest in competitive swimming," he said. "It's something that Michael said he wanted to do four years ago, and he's certainly managed to do that."
Hoarsell "Bunky" Colbert, the 52-year-old manager of the Druid Hill Park Pool, said people just can't stop discussing Phelps and his accomplishments.
"It's what everybody talks about when they come into the pool," he said. "We've talked about the relay where we beat France and how far Michael Phelps torpedoes under the water doing dolphin kicks when the rest of the swimmers are already above water and he's still down there looking up at them. ... It just makes people more excited about swimming, especially the young ones who are just learning."
Count Jordan Kasoff among that crowd.
The 8-year-old Owings Mills boy swims with the North Baltimore Aquatic Club's Tomatoes, the team for kids ages 5 and older, where Phelps got his racing start.
"I just learned how to dive off the side, and I'm practicing diving off the blocks now," he said. "This year, I started to become fast, and sometimes, when I'm in a good mood and a happy mood and a confident mood, I try to swim fast and good like Michael Phelps."
Todd Mackall, 17, of Stoneleigh, has spent his last real week of summer vacation - soccer practice starts tomorrow at Towson High School - in front of the television.
"Usually, I'd be out doing other things - playing sports with friends or going to see a movie," he said. "But I've been staying in to watch the Olympics just to see Michael."
Under a hazy nearly full moon, dozens of swimmers and fans gathered Wednesday night at Meadowbrook to celebrate his success.
Children dueled on the pool deck with inflatable bam sticks. With the cameras of Chinese and American network news crews rolling, they cheered with glee as Phelps finished first in his semifinal for the 200-meter individual medley. And they admired the medals of Olympic champion Brooke Bennett, who won a total of three golds in 1996 and 2000.
"I felt the gold medal," said 9-year-old Sophie Waterman, who swims with the Hunting Hills club in West Baltimore. "They look a little small on TV."
Like many of her friends, 15-year-old Ellie Burns of Phoenix has been staying up late to watch the races - despite having to be at a baby-sitting job at 8 o'clock each morning.
"I don't want to miss it," said the competitive swimmer, who often trades late-night text messages with friends about Phelps' swims. "I don't want someone to tell me the next day what happened. I want to experience it first."
It's not only the kids who are glued to the live broadcasts.
Janice Damon, 52, an administrative assistant at Johns Hopkins Hospital, has discreetly worked out a little scheme to avoid missing even Phelps' preliminary races for which there are no medals at stake. Upon hearing that a race is about to start from her husband - a schoolteacher, who has the summer off - Damon slips away from her desk and heads for a TV in the hospital waiting room or a prep room. Because the races are so quick, she's back to work in no time.
"There are no words to describe what's going on," said Damon, who got to know Phelps and his family when she worked at Towson High School. "To know someone just going to the Olympics is so absolutely incredible and exciting. ... But this is just hard to explain. ... It's so motivational and he's just so Michael."
Marie Rooney, a Middle River woman who owns a company that installs above-ground pools, also couldn't be more impressed with him. She and her husband were having their worst year in more than three decades in business when hundreds of thousands of Marylanders tuned in to see Phelps race - and her phone started ringing again.
"I think the visual of seeing so much excitement about swimming combined with higher summer temperatures, it makes people think about having a pool," said Rooney, who goes by the nickname of Mrs. Dig-M, an offshoot from her company motto: "You buy 'em, we dig 'em."
"I watched when Mark Spitz did it, and this is like, wow," she said of Phelps. "I heard someone say the other day that it's almost like he's Hercules. And it really is, to be that physically fit and accomplishing what he's doing. I just wish it wouldn't stop."