When Kendall Williams let her daughter, Bailey, paddle happily in a swimming class on the South Side of Chicago as a preschooler, she noticed the other parents seemed anxious.

“I don’t think any of them knew how to swim,” Williams said. “And they were afraid of the water and afraid for their kids.”

Williams, 45, and her daughter are African-American, as were most of the other families at the swimming class. While Bailey, now almost 9, swims competitively, most of the other children dropped out of the program.

Williams’ experience reflects one of the more intractable racial divides in American sports and culture. In the United States, a substantial majority of African-American young people and adults cannot swim or are weak swimmers, according to the most recent research from USA Swimming, the sport’s national governing body.

It is a trend that has a complicated history, including segregated swimming pools and beaches, attacks against African-Americans at pools as well as socioeconomic forces that divided access to swimming pools along class lines.

But now there is Simone Manuel, the charismatic young Olympic swimming champion whose stirring, surprise victory in the 100-meter freestyle in Rio de Janeiro made her the first African-American woman to win individual swimming gold. Her overnight popularity has public health experts and swimming advocates hopeful that she may have the star power to close the gap and inspire more minority children to learn to swim.

The stakes could not be higher, since not being able to swim can be a matter of life and death. Yet in the United States, it is estimated that about 70 percent of African-American children and adolescents cannot swim an entire length of a pool by themselves, a standard measure of swimming proficiency, and about 15 percent of these nonproficient swimmers cannot swim at all. By contrast, only about 6 percent of white children and teenagers cannot swim, according to data from USA Swimming.

The consequences are devastating. African-American children and teenagers are almost six times as likely as white children to drown in a swimming pool, according to statistics from the Centers for Disease Control and Prevention.

Several years ago in Louisiana, six African-American boys and girls drowned, some trying to save the others, after one of them slid into deep water in a river. None could swim. A friend of the victims, who also could not swim, helplessly witnessed the tragedy, telling reporters, there “was nothing I could do but watch them drown, one by one.”

The 2010 report commissioned by USA Swimming and based on surveys and interviews with almost 2,000 parents and children around the country found that many African-American families remain profoundly suspicious of and even frightened by swimming as an activity.

Some of this anxiety is attributable to old Jim Crow laws, which restricted many pools to “whites only,” the study’s authors believe. As a result, many African-American families avoided swimming pools and, in the years since, did not enroll their own children in learn-to-swim programs.

The 2010 report found, in fact, that if a minority parent had never learned to swim, the chances were less than 1 in 5 that his or her child would be comfortable in the water.

Carol Irwin, an associate professor of health studies at the University of Memphis in Tennessee, who was a co-author of the report, said many of the African-American parents and the young people who were surveyed for the study told the researchers that their fear of the water and of drowning was the primary reason they did not want to learn to swim.

This attitude has deep historical roots, said Jeff Wiltse, the author of “Contested Waters: A Social History of Swimming Pools in America.” A surge in the building of public swimming pools across America in the 1920s and 1930s attracted tens of thousands of new swimmers and set off the first recreational swimming boom, but these swimmers were almost exclusively white. Public pools often barred black swimmers, and many pools were situated far from minority neighborhoods.

“The few pools open to blacks were small, poorly equipped, and often located in places like the basements of buildings,” said Wiltse, a professor of history at the University of Montana.

A second swimming boom in the 1950s and ’60s occurred with the construction of thousands of private swim clubs in suburban America. Not explicitly closed to minorities, the pools were, however, a catchment system for affluent children, most of them white.

“You had multiple generations of white families who had a cultural tradition of swimming and passed that interest to the next generation,” Wiltse said. “And you had multiple generations of African-American families who had no comparable tradition. Instead, their experience of swimming typically involved exclusion and, more dramatically, drowning. For generations of African-American families, swimming has been associated with fear.”

Ebony Rosemond, who founded the website blackkidsswim.com, said that beyond segregation, there has been a history of violence against black people who ventured to beaches and pools.

“When I was growing up, we all heard about the black kids who got beat up or held under water if they tried to go to public pools,” she said. “People threw stones at black kids who went to the beach. There is this legacy of fear that got to be associated with swimming, and it wasn’t just about drowning. It was also about being attacked and driven away.”

Last year, Rosemond created her website because when she and other parents of young African-American swimmers searched online for “black kids swim,” the only sites that came up were about drowning or racial episodes at pools. She wanted to provide resources that were “positive, not just about drowning.”

One of the most common questions she gets is about hair. Concerns about the effects of chlorine on African-American hair are in fact so pervasive among girls — it was among the top reasons girls cited for not swimming, according to the 2010 report — that the website devotes a page to the topic. Its advice includes always wearing a swim cap, going natural, using anti-chlorine shampoo and conditioner after every swim, and perhaps considering cornrows.

A number of swimming programs are working to increase African-American participation. USA Swimming sponsors a program called Make a Splash that partners with local swim teams and cities to promote swimming among minorities by offering free or low-cost lessons and pool time.

Felecia Eaddy, 45, stood in line Monday at the Marcus Garvey pool in Harlem, waiting to sign up her 5-year-old daughter, Savannah, for swimming lessons. “My mother did not know how to swim,” Eaddy said. “She is 64 years old and she still doesn’t know how to swim, and I want to break the cycle with my daughter.”

Eaddy plans on bringing Savannah back as frequently as possible to develop swimming skills for “survival,” as well as exercise and confidence. “I encourage my daughter to be strong, and I think it’s important especially for girls to know they can do that as well,” she said. “Nothing about you can stop you, not your hair, your skin color, nothing.”

Joel Johnson, the president of the Chicago South Swim Club, where Williams’ daughter trains, fields a competitive team that is made up almost exclusively of young minority swimmers, and has produced several state champions. For these athletes, Johnson said, the experience of becoming first comfortable and then swift and strong in the water is “very empowering.”

“After watching our kids race, no one can hold on to the stereotype that African-Americans can’t be good swimmers,” he said.

The Annual Black History Invitational Swim Meet in Washington this year hosted the largest contingent of minority swimmers in its 30-year history, according to Gwendolyn Crump, the director of communications for the city’s Department of Parks and Recreation. More than 1,100 minority swimmers from 25 teams attended the three-day event.

The success of Manuel, along with Ashleigh Johnson, the African-American goalie for the U.S. women’s water polo team, and other minority Olympian swimmers reminds young African-American swimmers of what is possible, Johnson said.

“I sent out a message to all of our swimmers and their parents to watch Simone and the other African-American swimmers and athletes at the games,” he says. “I wanted them to think big about their own futures.”

Williams and her daughter dutifully cheered as Manuel won her 100-meter gold and then, on Saturday, won the silver in the 50-meter freestyle and a second gold anchoring the medley relay.

“Bailey was very happy,” Williams said. “But it wasn’t because she was inspired, exactly.” Instead, she had her expectations confirmed, Williams said.

“She was happy that everyone else was so happy, but she told me that she already knew in her heart that African-American girls can win gold, because she’s planning to do it herself.”

© 2016 The New York Times Company