The calm, clear water beckoned Caeleb Dressel, who stripped to his swimsuit and jumped into an unoccupied lane for the 6-and-under boys’ 25-yard freestyle race. Upon reaching the other side of the pool, he climbed out of the water and cried: “I won a medal! I won a medal!

In the stands, his mother, Christina, was mortified. Her son had not been entered in the race. He was at the River City recreational league meet in Jacksonville, Florida, to watch his brother, Tyler, who is five years older, compete for Chimney Lakes.

“I die laughing when I think about it now,” Dressel’s mother said, “but at the time I remember going, ‘Oh, my God, my kid just jumped in the water.’ I had no idea what possessed him to do it.”

Dressel’s leap into competitive swimming foreshadowed a career awash in medal-winning performances, most recently at the Southeastern Conference championships in Missouri, where he set American records in the 50- and 100-yard freestyles and the conference record in the 100-yard butterfly as his Florida team won the men’s conference title. His days of being able to hop in a lane and race anonymously are long gone, and that looms as his greatest challenge as Dressel, 19, prepares for the NCAA Division I championships in Atlanta from March 23 to 26 and the Olympic trials in Omaha in late June and early July.

Dressel, last year’s NCAA champion in the 50-yard freestyle, will invite more scrutiny this week as he leaves the cocoon of college’s 25-yard courses to compete against the likes of Nathan Adrian, the reigning Olympic champion in the 100-meter freestyle, at the Arena Pro Swim Series event in Orlando, Florida, in a 50-meter pool.

Gregg Troy, the Florida coach, acknowledged that there was a risk in having Dressel race in long-course meters when his focus has been on short-course yards. It is akin to throwing a stock-car driver preparing for the Daytona 500 into a Formula One race.

But with the U.S. Olympic selection meet on the horizon, Troy wants Dressel to gain experience racing against a quality long-course field. For all the fanfare created by his jaw-dropping times at the conference championships in the 50 freestyle (18.23 seconds) and 100 freestyle (41.07), Dressel is a relative neophyte on the world-class stage. His greatest exposure to global competition was the 2013 junior world championships.

Shortly after returning from that meet, held in Dubai, United Arab Emirates, Dressel abruptly quit the sport because he felt burdened by expectations. In an interview before a recent practice, Dressel likened his relationship with the water to a marriage, filled with highs and lows but rooted in an abiding love.

This tangle of emotions was encapsulated at one of his first swim lessons after that impromptu race from his youth. The instructor, Sean Scott, demonstrated how to do the butterfly. It is one of the harder strokes for beginners to grasp because of the timing of the double-arm pull and the kick.

Dressel, the third of four children, found his rhythm after only a couple of attempts. “That’s when I realized he has a gift,” said his mother, who was watching from the pool deck.

The lesson is Dressel’s first memory of swimming. “I cried,” he said. “I didn’t want to learn the butterfly because it’s hard. I got it right away, but I didn’t want to do it.”

Like the hull of a ship, Dressel’s body seems built to float. He is 6 feet 2 inches, with big hands and feet, and he naturally rides high in the water, which means he does not have to expend energy to maintain an ideal body position.

He also has an intuitive feel for the water. Jason Calanog, who coached Dressel with the Bolles Sharks in Jacksonville, Florida, encouraged his swimmers to keep workout logbooks. Dressel’s entries, Calanog said, contained detailed descriptions of how his body felt interacting with the water. It was not unusual, Calanog added, for Dressel to hop out of the pool in the middle of a workout and write notes in his logbook or, later, on his cellphone while a thought was fresh in his mind.

“His entries were definitely at a higher level than I’ve ever seen by a swimmer,” said Calanog, now an assistant men’s coach at Texas A&M. “He’d write pages and pages about how every muscle felt and what he wanted his stroke to feel like.”

Dressel was the youngest male competitor at the 2012 Olympic trials at 15, finishing tied for 145th in the 50-meter freestyle and tied for 152nd in the 100 freestyle, and as an age-group swimmer, he rewrote the record books, breaking a few marks held by the 18-time Olympic gold medalist Michael Phelps. Dressel’s age-group career culminated with milestone records in the 17-18 boys’ category when he became the youngest swimmer in U.S. history to break 50 seconds in the 100-meter freestyle and the youngest to break 19 seconds in the 50-yard freestyle.

And then, early in his senior year of high school, shortly after orally committing to Florida, Dressel left the sport. For six months, he did not get into the pool.

It was actually the second time he had taken time off. When he was 6, he and his two older siblings took a hiatus after Dressel’s father, Michael, was found to have Stage 4 sarcoma.

“The doctors said it was terminal,” Dressel’s mother said, “and I said, ‘We’re concentrating on Dad while he is going through this.’”

Dressel’s father, a veterinarian, made a full recovery.

Years later, Dressel was not sure if his swimming career would ever be resuscitated

“I had no idea if I was going to come back or not,” said Dressel, whose joy had been wrung dry. “As a 17-year-old kid, people put you on this podium, and it seems like you’re just a source of entertainment for people. I felt like I was swimming for other people and they’d never be satisfied.”

The “other people” to whom Dressel referred were not his parents, whose support has been steadfast. When he broached the subject of quitting, he said, his parents told him they would love him whatever he decided to do.

His mother recalled a conversation she had had with the three-time Olympic breaststroker Brendan Hansen that proved instructive. She said he told her, “The best thing you can do for your kids is put away your stopwatch and let it be their sport, not yours.”

The “other people” were not Dressel’s college coaches, either. “They were all very patient with me,” Dressel said, adding, “It was very calming.”

The “other people” are strangers on the Internet. Dressel’s ascent has coincided with the rise of social media, where every person with access to Twitter has the equivalent of a megaphone. That sharing economy did not exist when Ryan Lochte, the former Gator to whom Dressel is often compared because of his versatility and his success, was Dressel’s age. Lochte completed his collegiate career in 2005, the year before Twitter was created.

Troy, the Florida coach, said of Dressel: “He was almost out of the sport because he was such a good swimmer in high school and so many people were on him on social media about how good he was going to be, he got to the point where he thought he had to be something special all the time. So our challenge at the moment is to protect him from that happening again.”

Dressel is not worried. Swimming has become insular for him.

“It’s just me and the water,” he said, “and I’ll share the water with my teammates.”