Brruce Gemmell coaches Nation's Capital Swim Club athletes at the Georgetown Prep pool in North Bethesda. (Katherine Frey/THE WASHINGTON POST)

It’s winter in Washington. That means the temperature is often in the 40s during the day and below freezing at night. So it’s a good time for a swim!

More than 30,000 kids swim in leagues during the summer. But some kids keep swimming during the cold winter months.

Last week, I checked out the Nation’s Capital Swim Club. The club has 10 locations for winter swimming and has produced lots of top-notch college swimmers and five Olympic gold medalists, including Katie Ledecky from Bethesda.

Of course, no one wins a gold medal right away. The youngest members of the club start slowly. The 8-year-olds practice for about an hour three days a week. An older group — the 9-to-12-year-olds — has four or five practices a week.

Things get even more serious as kids get older. Top high school swimmers can spend up to 20 hours in the pool each week and a couple more hours doing “dry land” conditioning. Some workouts start at 4:30 in the morning!

Still, the club does not want to overwork its swimmers, especially the youngest kids. “We do not want to make 10-year-old national champions,” says Tom Ugast, who runs the Nation’s Capital Swim Club.

Tim Kelly, the head coach of the club’s American University site, agrees: “A great 10-and-under swimmer does not usually make a great 16-and-under swimmer.” Kelly, who swam at Southern Illinois University, sees his job as preparing swimmers to compete in college.

He appears to be succeeding. Around 75 swimmers graduate from the club each year, and most go on to swim in college.

So what makes a good swimmer? Kelly is quick to answer: “Someone who is not afraid to work. The best swimmer is not always the most gifted.”

Tammy Lowengrub, a coach at the American University site who swam for four national championships at Kenyon College, points out that Katie Ledecky “has beautiful strokes, but she has a great work ethic.”

Also, according to Kelly, a good swimmer is not afraid to fail. There are times when a young swimmer does not make the time he needs to move up to the next level of competition. The swimmer has to get back in the pool and try to improve. “Good swimmers are always working on their technique,” Kelly says.

One more thing: “You have to be excited to be here,” Lowengrub says as she encourages her young swimmers. “You have to think: I’m staring at the bottom of the pool, but I’m excited.”

Fred Bowen is the author of 18 sports books for kids. He has written books about baseball, basketball, football and soccer. But none about swimming.