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.