A recent Sunday afternoon at the normally sleepy Loch Raven reservoir played out like an episode of "Cops."

At its eastern point, a young man and woman who had been hiking made their way down to the infamous Loch Raven cliffs and jumped into the calm, beckoning waters to cool off.

They were blissfully unaware that across the water, reservoir ranger Simon Phillips was watching, just waiting for the 'splash' to spring into action.

"We have swimmers in the water," Phillips radioed a fellow ranger and jetted off to cite the swimmers $200 each.

This summer, this will be a common occurrence at the city's three reservoirs — Loch Raven, Prettyboy and Liberty. The rangers have the most members — seven — since they were brought back from a long hiatus three years ago and they'll be especially on guard for those trying to sneak in a dip.

With more forces, warnings and citations have been increasing, and last year peaked at more than 2,500 just for illegal swimming. Phillips hopes the combination of heavier enforcement, fines, more "no trespassing" signs, and word of mouth will begin to discourage swimmers.

"People see it as a park. It even comes up as a park on Google. They think, 'if if it looks like a park, it feels like a park,' then it must be a park. What we do every year is try to convey to people these are not parks," Phillips said. "What more can we do to explain to people, 'we don't want you beyond a certain point."

Though illegal — the reservoirs are a source of drinking water for some 1.8 million consumers — swimming at the reservoirs is a Baltimore tradition.

The lush forests surrounding the watersheds, what rangers call "the buffer," have the makings of a natural, recreational haven.

"I spent my senior spring break here. I might have even brought a date. We just packed up a picnic and went swimming," said Sheila Korman, a dental hygienist from Sparrows Point who was wading with her husband and two children at Loch Raven's so-called Pines Sunday.

Combined, the reservoirs cover over 24,000 acres of land and water, an enormous area where thousands have been going for decades to picnic, mountain bike, hike, bird watch and fish.

During the summer, the rangers also see increased drug use, alcohol consumption, and late-night mountain-biking. But it's the swimmers that become enemy No. 1.

The nearly 500 squared miles of combined watershed area have been a magnet to locals for years, and there are scattered traces of them hidden everywhere. At one of the cliffs on Loch Raven's southern point, tattered, jaundiced ropes used by swimmers to jump into the water hang from the trees.

"People have been jumping off the cliffs for decades," Phillips said. "When we get to the peak of season, we could have 30 people in the water at any point."

About 100 people transit through the Loch Raven cliffs on a weekend day during the heart of the busy season, which typically starts in late June, Phillips said.

On Sunday, he waited for a boat ranger to escort the swimmers to the top of the cliffs.

Andrea Watson and her friend, Michael, a gangly, 22-year-old who just graduated from Johns Hopkins University, had spent two hours hiking around.

"Then a whim took us and we went swimming," said Watson, a 23-year-old who moved to Baltimore from California three weeks ago. "It's been so hot in town lately. We needed an escape." Michael declined to give his last name.

After jumping from a foot-high cantilever, the water was nirvana.

"It was so nice. It was perfectly warm on top for the first three feet, and then you dip your feet down and it's just icy cold," she said.

Although they told the boat ranger, Cyras Phillips — no relation to Simon — they knew they weren't supposed to be swimming, Michel asked Phillips for a break.

"I'm not prepared to do that," he said. "We have far too many people violating these rules for me to let it go as a warning. I know it's frustrating to get caught, but we're all adults. We make choices and there are consequences."

In the three years Phillips has been on the job, he says he's heard all kinds of excuses, and none of them make sense, especially "I didn't know it was illegal, officer."

"When you come to an area that's privately owned, the onus is on you to find out what you can and can't do," he said.

Swimming, as a potential pollutant, has been banned here since at least the 1920s, said ranger Luke Brackett.

The City's Department of Public Works, which funds the rangers, also warns that the waters can be treacherous, and most swimmers aren't aware of the currents or the quick change in temperatures when they dive into depths of as much as 90 feet.

Last year, three men drowned, including a 23-year-old Havre the Grace man who went under as he was attempting to cross Loch Raven reservoir.

"Everybody knows its illegal, and why its illegal," said Kurt Kocher, department spokesman. "It's not a swimming pool. There are legal places where you can go swimming. These three reservoirs are for drinking."

Rangers have wide latitude to enforce watershed regulations, and also criminal and traffic laws — a typical enforcement log from May ranged from the mundane — destruction of property — to serious crimes — possession of a controlled substance, outstanding warrants.

"We're here to protect people from the resources, the resources from the people, and the third thing we do, is protect people from people," Phillips said. "We're trying to convey to the public these are not parks"

Swimmers are by far the leading source of concern, with trespassing a close second, according to Public Works.

Though the 24,000 acres they have jurisdiction over can be daunting for their small staff, the rangers have been incrementally ramping up the fines.

Last year, 2,254 people were given verbal warnings not to swim, 279 were cited and two people were arrested for "swimming and related activities," according to Public Works.

This past May alone, 207 were given verbal warnings by the rangers, and 28 people were cited.

There are other deterrents: "No trespassing" signs, of various sizes, are widely posted. Fines start at $100 for swimming, wading and trespassing, and, if the rangers choose to process a violation as a misdemeanor, they can be as much as a $1,000. Polluters are given the stiffest fine, $500.

All that money ends up at Public Works, which could not provide a total amount. Kocher said it's a small amount in relation to the rest of their revenue.