When Denise Dombay opened a Montgomery County swim school in September, the first-time business owner thought it would fill a void. Now, she knows it.

The Maryland mom, a college swimmer with a 30-year finance career, brought Denver-based SwimLabs to Gaithersburg last fall as the franchise’s 14th location. Six months later, her space at 353 Muddy Branch Road sees about 400 beginner and competitive swimmers for lessons — and she expects that to double by summer.

Dombay is preparing for heightened demand because parents want their kids to be pool-ready for camps and vacations, and the start of the popular Montgomery County Swim League means thousands of swimmers seeking training, she said. That surge likely wouldn’t slow down until August or September.

To handle the influx, Dombay is booking clients and hiring staff, adding more competitive coaches and experienced instructors to her 25-person team, she said. That could grow to 35 or 40 employees once at full capacity.

The 6,000-square-foot…