Steve Webster stands in water up to his trim waist, a lifeguard's whistle dangling from his neck. A small girl flops onto her belly in the water next to him and disappears except for flailing arms and kicking feet.

"Swim, child! Come on! Keep your big head down! Come on, little one!" Webster yells.

It's a summer ritual, morning swimming classes at the Kenilworth-Parkside outdoor pool, 4300 Anacostia Ave. NE. Webster, manager, lifeguard and sometime-instructor, is encouraging a group of squirming children, ages 4 to 9, to do something he never did at their age: swim.

Webster, who is 33, was a 22-year-old District police officer when he took his first dip in a city pool. "My sister bugged me every morning about going swimming," he recalled. "So finally I took lessons. I'm still not a great swimmer. But I have good techniques and almost every certificate the American Red Cross gives."

In fact, he's a Red Cross certified teacher of water safety, first aid, cardiopulmonary resuscitation instructors and adaptive aquatics instructors, who teach the physically impaired.

He's reaching the end of his fourth summer at this outdoor pool in far Northeast. During the winter, he manages the Marie H. Reed indoor pool in Adams-Morgan.

"At Reed, I smell chlorine all day," said Webster. "Here I have the sun and the fresh air. I love it. Here I have a lot of children, too."

Nineteen small heads face him, their chins resting on the pool's rim, the bodies that belong to the chins submerged under water. He stands on the edge of the pool facing his class.

"Kick," Webster commands, and 38 feet flutter, splashing water.

"My legs are tired," one boy begged.

"Okay, stop!" said Webster.

Lifeguard William Gressen, 19, assists. It is his first summer at an inner city pool. Gressen, who is a University of Maryland student, also works at Theresa M. Banks Memorial Swimming Pool in Glenarden, where Webster saw him on the job, and recruited him for the District.

"Basically, I just love the water and this is the only way I get to be around it all the time," said Gressen, who learned to swim at age 9, after buddies threw him into a river.

"I've never taken a swimming lesson but I took the Red Cross courses because I went to military school, and we had to take them to graduate," said the six-footer. "Still, we didn't get in the water; we diagrammed the side strokes and flutter kicks on paper."

The older instructor considers Gressen "mature, well-mannered and courteous. I want kids who listen, pay attention and are fairly mature," said Webster, who generally recruits from the students he teaches in his Red Cross certification classes.

Lifeguards must be at least 16 years old and have certificates showing that they've taken at least 21 hours of advanced lifesaving courses. In the District, in addition to certificates, lifeguard applicants are given rigorous tests including timed laps and the execution of a mock rescue.

The District's Aquatics Division of the Department of Recreation estimates that there are more than 900,000 visits to the city's 45 pools each year, said Benny McCattry, chief of the division.

"At any one minute, with every pool at capacity on a hot day, we could be swimming 16,000 people," said McCattry, noting that there has not been a drowning in a supervised city pool since about 1978.

The 33 outdoor pools, which opened since June 6, will be closed by the end of the Labor Day weekend. The 125 additional lifeguards will leave, most returning to college, and 50 full-time lifeguards will remain to work in the indoor pools.

Kenilworth-Parkside, with 40,000 visits a year, is considered one of the busiest pools. Webster has a staff of eight lifeguards. On a typical day, 11 swim classes meet, a swim team practices at noon and the pool is open to the public from 1 p.m. until closing, at 8 p.m. on Mondays, Wednesdays and Fridays and at 6:40 p.m. on Tuesdays and Thursdays. The pool is open from noon until 7 p.m. on Saturdays and Sundays.

Gressen spends days at Kenilworth-Parkside, then goes to his other lifeguard job in the suburbs, where he helps supervise activities that include night pool parties.

"Being a lifeguard is ideal for me because I love the water and love working with people, especially kids," he said. "I like seeing the kids come here terrified and leave confident. We learn to trust each other and by the time they leave, they're sharing all their secrets with you."

On this morning the children hold each others' hands and follow Gressen around the pool, always staying away from the edge, until they reach the deep waters, the 12-foot end.

"Okay, now watch me," said Gressen, stepping off the edge of the pool to plunge into the water. He swam several feet, then yelled, "Are we ready?"

One small boy's voice could be heard above the others: "No!"

Gressen let those who felt timid wait on the sidelines and watch their classmates.

Gressen said that although some young men may think of a lifeguard job as a chance to flex muscles and win the admiration of young women, "It's much more. We don't have a cleaning crew, so we have to clean up, too. People are shocked when they find out that because they think this job is all glamor. Also, there are the knuckleheads and the nerds, but you have to talk to all people with respect . . . .

"And at every pool, there are girls looking for hunks in the chairs," he said, shrugging. "But this job is a service to the public. There's really no time to pay attention to the girls. You have to know how to do your job first, then talk to the girls later."