These days, it is common to see Joseph Schooling, the target of at times over-zealous fans, surrounded by at least four imposing security officers at public events here.
But the Olympic champion can probably hold his own now, after undergoing a mixed martial arts (MMA) crash course with a fellow champion.
Angela Lee, One Championship's atomweight world champion, put the swimmer through the paces yesterday at Evolve MMA, teaching him several striking and grappling techniques in a 30-minute session.
They were joined by Lee's brother Christian and Schooling's team-mate from the University of Texas swim team, Tripp Cooper.
Swopping goggles for gloves and trading his powerful underwater kicks with a front kick, Schooling acquainted himself with several striking combinations and takedowns.
A fan of MMA star Conor McGregor, he also asked the Lee siblings to teach him how to unleash an upper cut.
Lee, who at 19 is MMA's youngest world champion, was impressed.
Trained in several martial arts forms including Brazilian jiu-jitsu and taekwondo, she said: "Joseph did a great job today. He's a really fast learner and did a great job executing the technique. I had a lot of fun with them."
Asked if he would incorporate the workout in his training routine, Schooling said: "It's really good cardio. We were here for what, 15 to 20 minutes and I'm already sweating.
"We used to do a bit of shadow boxing in training for cardio. I won't step into a ring, but yes, definitely I could do some MMA stuff during training."
He also attended a Make-A-Wish Foundation event at Kallang Wave Mall in the afternoon. There, he ferried three children around the area in a Porsche.
The Make-A-Wish Foundation grants wishes of children with life-threatening illnesses. The swimmer will also donate some proceeds from the sale of his picture book Hello, My Name Is Joseph Schooling, and of limited prints to the foundation.
•Additional reporting by Nicole Chia