His chlorinated domain of cool, blue water stretches far and deep.

His laws are simple: No running. No diving. No horseplay.

For three months out of the year, Robert Davis, 13, waves his arms, puts his hands on his hips and cracks commands at the kids who come to the Anacostia public swimming pool in Southeast Washington, where the "junior lifeguard" has come every summer day since he was 9.

"Hey! No running!" he screamed at two boys a little older, taller and thicker than he is.

"Sometimes, it's hard to tell people what to do," Robert said, sighing.

It was easy to tell his mom that he didn't need pool money anymore, though: "Yeah, she was pretty happy when she heard about that."

In July, the District government lifted the swimming pool fee for children. That's $1 a day that Robert's mother has saved. He said it made her even happier to send him off to his aquatic kingdom, where he also is in charge of untangling and corralling the spaghetti of pink, yellow and blue pool noodles kids leave behind at closing time every day.

The savings went even further last week, when a $200,000 grant from Kaiser Permanente extended free admission to adults in all of the city's pools and ensured that they would stay open until Sept. 30.

"I went to my council member and said there has got to be a way to help families get free access to fitness and recreation," said Alicia Rucker, a D.C. mother of six who realized that for families like hers, paying $9 a day for admission makes swimming throughout the summer prohibitively expensive.

"Back in the day, when I was coming up, the public pools were free, so we all went," said Rucker, once a champion swimmer for the East Capitol Sea Devils. "Now, if parents have to pay for it, not all of them are going to send their kids to the pool. I bet we'd have a lot fewer kiddie car thieves if the pools were all free."

Pool manager Sean Link said that when there was no admission fee before 1997, the Anacostia swimming pool was packed with about 400 kids every day.

Since then, there have been a few neighborhood die-hards, but most visitors have been day campers who came to the pool in groups.

"I can see the difference this year, after they made it free. The neighborhood kids came back, lots of them," Link said.

Free swimming and 90-degree weather brought lots of splashing and swimming to the Anacostia pool yesterday. To put this summer's heat in perspective, the relatively temperate 90 degrees at Reagan National Airport led the National Weather Service to lift its heat advisory yesterday. Cloud cover had kept the heat down. "It's been a hot summer; we've had a heat advisory almost every other day," said forecaster James Brotherton.

The hot day and free admission gave Angela Woods an incentive to go swimming with her two children. "Anything the city can do for kids and for families is great," she said before giving her kids a rundown on the rules and they took off in the shallow end.

"No running. No fighting," said Woods, after being interrupted by a splash of water that hit her in the face. "Splashing is okay, I guess," she said, wiping her face and straightening her swimsuit skirt before heading back to her chaise longue and magazine.

Robert Davis, left, and Jerrel Jones cool off. With free entry, "neighborhood kids came back," says the pool manager.Brianna Marr, 9, finds a cool oasis in the sizzling heat. A $200,000 grant from Kaiser Permanente extended free admission to adults in all city pools.