They begin flocking to the rooftops and terraces at noon, carrying small totebags and wearing harried, tense expressions.

Disappearing into tiny locker rooms, they shed their clothing, their contact lenses and their cares.

They slither into swimsuits, slather on the Deep Tan, slip on their sunglasses and reappear on the rooftop - transformed for one precious hour from city workers on their lunch break to carefree sun and water worshippers.

Every sunny weekday, this "poolside lunch bunch" enjoys a short, but sweet splash 'n dash at one of the handful of District hotels that offer summer memberships at their swimming pools.

L'Enfant Plaza Hotel, The Executive House, The Washington Hilton, Skyline Inn and Marriot Key Bridge all offer swim club memberships ranging from $75 to $425 for the season. The Gramercy and Connecticut Avenue Holiday Inns attract occasional "lunch bunchers" with their $2-a-day rates.

Some go for the exercise, diving into the water with the enthusiasm of children. Some are there just for the sun, sinking into lounge chairs and not coming up. But they're all there for the relaxation.

"It's like an oasis in the middle of the work day," grinned Mike Seymour, a trim half-mile-a-day swimmer, who says it takes him only six minutes to get into the water from the time he leaves his office at the Department of Housing and Urban Development.

Lounging around the pool is "addicting, an escape, a fantasy," said bikini-clad Becky Kennedy, who packs her wet bathing suit in a zip-loc plastic bag before returning to work at the Environmental Protection Agency. "On days that it's cloudy, I spend all morning looking out the window to see if I'll get to the pool at lunch."

"It breaks up the daily routine," sighed suntanned Barbara Buckheit, a computer systems analyst for the IRS, as she sipped a fruity cointreau and rum concoction called A Touch of Class. "The sun, fresh air and swimming leaves you feeling completely refreshed."

Some industrious sunbathers bring their work to the pool.

"Somehow this reads a lot better here," admitted a sleek Department of Energy worker as she held an excerpt from the Congressional Record on her lap. "It's so relaxing here that sometimes I forget that I'm at work."

One wet embassy staff member said he hangs his swim trunks on a hook behind his office door and covers them with a raincoat. He preferred to remain anonymous so his boss "wouldn't get the idea his staff is sitting in the sun all day."

Film editor George Singer said he enjoyed the city pool scene so much that he arranged to work at night so he could spend seven days a week at the pool.

"It's the next best thing to being in the jet set," laughed 45-year-old Singer, one of nearly 700 people who are members of District swim clubs. "You go up a couple of steps to the pool, and you're in a different world."

The relaxation and exercise helps some lunchtime lappers return to the office refreshed and ready to tackle the afternoon's work.

"I get all my anxieties over with for the morning so I'm ready for the afternoon," said the U.S. Railway Association's Bob Finley, who swims 48 laps every other day.

"It helps you keep your sanity." HUD attorney Gains Hopkins grinned from behind bright green goggles. "Swimming a mile a day instead of eating lunch makes me more relaxed and more effective at work."

Sitting in the sun also keeps pool members from squandering cash at summer sales.

"It's too hot to sit in the park, so I'd be in the stores spending money if I didn't come to the pool," said Valerie Blitgen, who works at National Geographic. "Also, it's a great place to come after work if there's too much traffic."

About 1 p.m., the back-to-work exodus starts. Locker rooms become crowded with rushed, frantic bodies pulling on suits and shoes, blow-drying hair and making last minute mascara repairs.

By 2 p.m. only hotel guests and a few straggling lunch bunchers are still at poolside. L'Enfant Plaza lifeguard Julia Daniel can finally grab some lunch, after the 11:30 a.m. to 1:30 p.m. pool rush hour is over.

But one of the stragglers is still lounge-bound. Peeking out from under a brightly colored sun visor, the darkly tanned lounger sighed, "It's so relaxing and refreshing that I just hate to go back to work."