Mary “Mae” Jackson, 93, has become a celebrity of sorts at the National Senior Games at Stanford University in Stanford, Calif.

On Sunday, Jackson won a gold medal in 200-yard backstroke in her age category, 90 to 94. On Tuesday, she won the 100-yard backstroke, three seconds off the Games’ record. The longer distances are her strongest, but Wednesday she was set to test her strength in the 50-yard backstroke.

Jackson is no stranger to the water, having learned to swim in the Charles River and having later coached a youth swim team at the South Shore YMCA in Quincy. The winning is new to her, though. She only started competing two years ago, at age 91.

“I can’t believe it – at my age that all of this is happening,” Jackson said Monday night.

After the Senior Games, she will have another celebration: her 94th birthday on Friday.

Her granddaughter Jennifer Ericson, 42, of the San Francisco Bay area, a former competitive swimmer, is her companion and coach.

Ericson’s college friends cheered from the stands, wearing “Team Nana” T-shirts.

“She’s such a wonderful soul and an inspiration to many,” Ericson said. “In the 200-yard event, she had such a lead over the other swimmers in the younger age categories, the crowd went crazy. They knew her age, and afterward everyone was coming up and saying, ‘Congratulations, Nana.’”

A sports psychology professor making a documentary to encourage older women athletes filmed Jackson swimming and interviewed her.

“Nana is showing the other side of aging,” Ericson said.

Both her daughters, Martha and Meredith, and all her grandchildren traveled to the Senior Games to cheer her on. When it’s over, she’ll head home and resume her weekly visits to the Weymouth town pool.

“I like swimming. It’s wonderful for meditation and for the strength of the body,” she said.

Patriot Ledger writer Sue Scheible may be reached at sscheible@ledger.com.