Nowhere in the city does summer seem harsher than in Anacostia, the often-forgotten neighborhood across the river, where the heat bakes crowded housing projects and densely packed row houses, and the steamy haze only adds to an oppressive sense of back-street isolation and abandonment.

For Anacostia there is, yet, a tiny oasis of escape, a thin strip of grass and trees and promise between the river and the streets, and in this narrow green park, sparkling like the sea, is the pool.

The ritual begins each afternoon, when the children cross the foot bridge that takes them over the highway to the free city pool in the middle of Anacostia Park. The water is clear and clean; LeRon Goodrun manages the pool, and the recent University of the District of Columbia graduate and running back, who hopes this summer for a tryout with a professional football team, is a perfectionist about keeping it spotless. His eight lifeguards take their stations--seated in the big red chairs or standing along the cement sides--whistles ready, braced for the day's crowds, which on humid days hit the pool's capacity of 400 by 3 o'clock.

Each year there are new faces and new bathing suits and new games--this year they play variations of tag called Shark and Jaws, and something called Karate ("We go underwater and kick each other")--but the important things about this pool in Anacostia, or any public pool, don't change. There is the unmistakable summertime smell of chlorine which mixes, in the locker room, with disinfectant. There is the impossibly blue color of the water, reflected from the painted bottom, with the darker blue stripes for swimming laps.

There are the green net bags for clothing, which come with numbered safety pins that swimmers fasten to their bathing suits. The bags are kept by the locker room aides. This summer one of them is Donna Small, 26, who took a leave of absence from her job at District Line Liquors to work at the pool for $3.35 an hour. "I didn't want to be cooped up," she said. "Here I can be outside. I can swim."

On the boys' side is Anacostia High School assistant wrestling coach Wright Jolley Jr., who is thinking in this, his 22nd summer, of getting out of Anacostia, of doing something different, maybe joining the Marine Corps. "I grew up in Barry Farms projects," he said. "I got out, and I've been trying to help other people get out. I've been helping a lot of people for a lot of years and now I'm tired of it."

Outside, around the 50-meter pool, there is the sound of the transistor radio, playing the summer's hits. There are the accidents--the bee stings, the scraped knees and elbows, the bloody noses, the sudden cramps, the occasional non-swimmer who ventures into the diving area--all expertly handled by the lifeguards, who seem uniformly tall, handsome and stern. There is the constant shrill tune played on the lifeguards' whistles, signaling someone to stop running or dunking or pushing people in the water.

"I hate the lifeguards," 9-year-old Owusu Wilson said with feeling the other day, sulking because he was kept out of the pool for 30 minutes for running.

Each year there is one lifeguard whom every girl seems to fall in love with, and this year at Anacostia it is a dreamy-eyed 17-year-old in white trunks named Frank Hogan III. "Hey, lifeguard, you're cute," the girls say. "What's your name?"

"Fred," says Frank, who has no time for flirting on the job.

As indispensable as the lifeguards is Percy Poore, the private contractor who for 20 years has kept the city's outdoor pools properly filtered and chlorinated. He was there last week, checking his pumps, admiring the Anacostia pool, an old pool, he said, that was built in the 1930s, but still one of the best in the city. The day was sweltering, but Poore had no plans for swimming. "That would be like a bus driver taking a bus ride," he said, sweating. "This is a lot of aggravation, but it's worth it to see these kids enjoying themselves."

Mornings at Anacostia Pool--open Tuesday through Sunday--are for swimmming lessons and swim team practice. Adult swimming is in the evenings. In the afternoons the pool belongs to the children, who jump in the water at 1 and stay immersed until dinnertime, seemingly inexhaustible. Summer, says 7-year-old Kirk Taylor, brother of lifeguard Kevin Taylor, is for "eating plums and going swimming." A handful of grownups mingles with the splashing masses, among them Louis Williams, 50, who works the graveyard shift at the Government Printing Office. "I can't swim, I just cool off," he said. "I grew up in Columbia, S. C. We swam in the ponds there. We didn't have too many pools."

A plump woman in a flowered bathing suit sat on the cement steps beside the pool one afternoon last week, watching the children with a wistful smile, remembering her own childhoood here. The life of 33-year-old Tijuana Tabor, who grew up in public housing at nearby Barry Farms, is intertwined with this public pool in Southeast Washington as the lives of other people are tied to a camp in the mountains, a summer house at the beach or a certain secret place in the woods. Here is where she learned to swim, met her first boyfriend and taught her daughters to swim, and here, during her 21st summer, a hard, painful time, is where she spent endless afternoons floating on her back with her eyes closed, forgetting her hardships and searching for strength.

"I was born and raised in this pool," she said. "We used to come here every day in the summer. Everybody who came here knew everybody else. They had a snack bar then and a miniature golf course. We couldn't use the golf course. . . . It was for whites only. It was a dime to get in the pool then in the afternoons. In the evenings it was 65 cents."

She remembers a lifeguard named Jerry. "I think that was my first love. I was eight. He was gorgeous. One time I was just starting to learn how to dive. I dove in, and somebody swam right past me as I was coming up, and I couldn't breathe. He saved my life, and I fell in love with him."

In her 12th summer, she met a curly-haired boy named Butch Shorter. "We were both good swimmers. We used to come down here and sneak kissing underwater. We thought we were in love." She made up her own water ballet routines and dreamed of becoming another Esther Williams, the swimming movie star. "I wanted to be Esther Williams so bad. I would watch all her movies. She used to come on the late show, right after Steve Allen. I loved her."

In the summer of 1970 Tabor was struggling with a drug detoxification program. "I was coming off methadone. I was still feeling bad. I'd get in the pool every day and stay all day. It helped me to get through. The water made me extra tired. I'd come home, fix dinner for the kids, fix my dinner, and we'd just lay back and watch TV. The water helped me get my act together. This pool saved me."

Now, Tabor lives in Seat Pleasant and still swims at the Anacostia pool, a place of nostalgia and escape. She lost her job in March when the nightclub where she was a hostess closed, and she worries about paying her rent and her electric bill and about finding a new job. "When I come here, I put it all behind me," she said as the sound of children splashing and laughing filled the afternoon. "When you lay there on your back and you have your eyes closed and the water carries you, it's the best high in the world. All that tension, everything's that going on in the world is not there. This is my getaway."

As constant as the fragrance of chlorine and the sound of the lifeguards' whistles is the summer thunderstorm. There was one late in the afternoon Thursday, Tabor's day at the pool, and the lifeguards quickly got everyone out of the water. In wet bathing suits, the disappointed children made their exodus across the foot bridge over the highway, home to Anacostia. They would be back Friday afternoon, and all the afternoons after that, until Labor Day, when the pool closes until the next summer.