Imagine a cool night in Georgetown's fast lane; silk tuxedos and chiffon evening gowns flirting in a swirl past trays of caviar and smoked Nova Scotia, on out into the backyard where -- omigod! -- a number of guests have flung their formal dress on tree branches for a romp. . . in the hot tub.

Indeed, political charley horses are boiling away. No one is shouting. All is forgiven. The deal-making is, well, mellow. Enter the New Age of Hot Tub Politics.

It has yet to come to this, of course, but those who perch on the cutting edge of the social scene say it could. In California, hot tub togetherness long ago replaced the backyard barbecue, and nowadays, only drop-ins from the heartland blush at the notion of nude bathing among strangers. What's worth noting is the rapid pace that hot tub chic is moving east, where the formerly uptight in places like Des Moines, Chicago, Atlanta and, yes, Washington, D.C., are donning birthday suits to take the plunge.

Industry sources estimate that 30,000 redwood hot tubs were sold in the United States last year -- $60 million worth. (That's up from 5,000 tubs three years ago.) Stir in the 75,000 fiberglass spas that health-lovers snapped up to avoid splinters in the tuchis and you've got another $190 million in sales. That ain't just water down the drain, says Harold Cowley, a California spa manufacturer and head of the industry's fledgling trade organization, International Spa and Tub Institute. He expects sales to quadruple this year. "Every tub that's made is sold," he says. "We're backed up four to six weeks on orders."

At $1,500 to $2,500 each, hot tubs represent a growth industry that picks up where swimming pools left off. "The swimming pool is a dinosaur. Something had to replace it," says 29-year-old hot tub entrepreneur Cliff Branch, founder of the country's largest tub maker, California Cooperage. He claims to have brought hot tubs "to the masses."

"Pools," he sniffs, "are not in the spirit of the times. They're big, cold, impersonal, made of cement and cost $10,000 to $20,000. Hot tubs are small, warm, intimate, made of wood, relaxing, use less engery and cost one-fifth what pools cost.

"This generation is going to express its affluence differently. Possessions will reflect their social values."

Even though the image of the hot tub may be orgiastic -- steamy nights of banter and bacchanal -- the typical buyer is a white collar professional, a homeowner, 30 to 40 years old, married, a somewhat sophisticated individual for whom $3,000 usually means a quick, painless stroke of the pen. "Our buyers aren't hippies," says Branch. But he readily concedes that a number of wild and crazy guys probably salivate over their suggestive ads in Playboy and Penthouse and snap up the hot tubs "as a better mousetrap."

It's a way for this generation to experiment with nudity. A guy can tell his date, 'Hey, let's take a hot tub,' and the girl takes her clothes off in a second. It's no big deal."

One evening in Mill Valley, California, it was not big deal for writer Bill Barnes and his wife, Joan, an educational consultant, to invite friends over for wine, cheese and a hot tub. A brilliant orange sun was sinking into the Pacific as a neighbor's naked five-year-old boy yelled after the Barnes' two daughters to take off their clothes and join him for a bath.

Parents hardly notices. They were lounging beneath a mulberry vine, sipping Sebastiani Mountain Chablis and nibbling an oozing brie. In a few moments, the kids were sent packing, as moms and dads climbed in together.

"So what if we take off our clothes and flaunt it," said a 30-ish New York emigre to the coast who happened to be the five-year-old's mother. "Hot tubs are sensual, not sexual, like being in the womb. It's good, clean living. We lather up with peppermint soap and rinse off before we get in. And just sitting there is a high that's better than sex or drugs."

Such a casual, risque attitude, however, doesn't always mesh with conservative climes like Dallas or Washington, D.C., where hot tubs are being touted as therapeutic, a nifty family contraption, the ultimate path to relaxation. Some ads even show bathers in, yes, bathing suits.

Still, hot tub owners hereabouts consider themselves in the fashion vanguard. Local dealers and manufacturers claim to have sold tubs to the daring of Potomac and Chevy Chase, Falls Church and McLean.

John Kinscott, an EPA water resource engineer, spent $1,000 and a year scouring lumber yards to build his own hot tub from the bottom up. He planned to invite over friends to make the shakedown cruise in his back yard in Cabin John. "After a year of concerted effort, of course, you expect some kind of return," he said. "But when I fired up the mother I wasn't disappointed."

And radiologist Charles Boyle and his wife, Bonnie, a freelance writer, are said to number among Georgetown's hot tub pioneers, having installed a $2,500 redwood vat in their backyard. "I'm not going to be bothered by neighbors looking at me," insisted Mrs. Boyle who, by dark of night, has already inaugurated the six-foot tub with friends. One neighbor with a view has joked about installing a diving board.

To maximize privacy, though, the Boyles have installed a wooden fence about their bath, and begun to ponder growing a jungle, lest their communal soaks attract grown-up gawkers and curious kids. "I don't want to traumatize a child," she says. "I figure adults can take care of themselves."

The Boyles purchased their hot tub in the form of a kit from Charlie Edwards, a retired Atomic Energy Commission metallurgist who hawks California hot tubs out of Falls Church. Edwards, one of a half- dozen or so area distributors, invites potential customers back to the house for an au naturel demonstration with himself and his wife. The high and the mighty have eased into the swirling waters chez Charlie, he claims, but Edwards isn't giving out any names.

One bashful buyer, however, insisted on wearing a bathing suit -- yet to be washed free of detergent. The swirling water turned Edward's tub into a rinse cycle and, alas, upset the delicate PH balance.

When the Boyles knocked at his door, Edwards led them to the patio and instructed, "Now take off your clothes and hop in." The Boyles froze. "Well," said Mrs. Edwards, "if you want to be left alone,. ." And suddenly, the strangers became one big happy family.

"We hemmed and hawed at first," admits Bonnie Boyle. "There's sort of an orgy image about hot tubs -- that everyone will climb in and . . .But the water is usually so hot, it wipes you out."

At 105 degrees. a customary setting, friskiness is fast diluted. And there is the danger of soaking into a faint, should bathers fail to monitor themselves. In May, one California couple, a retired Navy captain and his wife, dozed off in a tub and became the first official hot tub fatalities. Edwards, who heads up Hot Tubs International, says in that case, the water was "much hotter than the manufacturers recommend." In fact, a Ventura County coroner's report confirmed that the water temperature measured 110 degrees one hour after the bodies had been found, and blamed the deaths on heatstroke, high blood pressure and excessive drinking. The Consumer Product Safety Commission is investigating the incident.

Hot tubs are the latest California Experience to float east like a wayward mushroom cloud. And if history repeats itself, social observers are musing that what evolved from a mid-60s incarnation as a grape-stomping wine vat could:

Replace the conference table as a forum for discussion:

force gossip columnists to scramble for their lives as a once-titillating milieu becomes, yawn, passe';

send old social understandings right out the window; and

require accepted codes of good manners to be rewritten.

All hell could break loose.

To bring about a calm transition to the new era, hot tub commanders suggest a few rules of the road.

Rule 1. It's fine to look all over, but don't stare. In their natural wander, eyes may come to rest on one spot: Urge them onward. It is considered poor breeding to register either lust or disgust. On the other hand, if the bather hops onto the rim of the tub to cool, you may suddenly find that your eyes no longer gaze directly into another's. It's polite to look up, up and away.

Rule 2. It's okay to touch tootsies, but only after being properly introduced. Should two feet find each other beneath the water, it could be a beautiful experience. It's all right to play -- even to give and receive a massage de pied -- but further intimacy should be left to develop naturally. Nothing is worse than a group-groper in the midst of mellow fellows.

Rule 3. Never complain about the color of the water. If it's yellow, assume pollen caused it. If you must inquire, do so obliquely: Ask how the filter works.

Rule 4. Never compain about the temperature. If you can't stand the heat, get out of the tub. There's good reason for this. (See rule 2.) Some tubbers turn up the thermostat after the fashion of fretful boarding school headmasters. Others, like veterans of the 120-degree Japanese "ofuros," just plain like it hot. Check the thermostat to find out where your host is at: 105 degrees is deemed a temperature that is friendly, but not too friendly. Below 105, camaraderie could bloom into true togetherness; 110 degrees is generally agreed to be "therapeutic." Anything hotter is guaranteed to take the starch out of any sail.

Rule 5. Splasing is poor form. If the tub is near a window, your host may have to spend the next day with a squeegie.

Rule 6. No passionate meetings in the flower bed behind the hot tub. Nothing annoys a green thumb more than finding tell-tale body prints in the posies.

Rule 7. In your search for more champagne, don't go tracking water into the kitchen. Towel off before you toddle off.

Rule 8. No eating in the tub. Chicken bones tend to float to the top, but it doesn't take long for them to get soggy, sink to the bottom and make a mess.

Rule 9. Always call in advance. Just becuase you've been invited over once, don't assume a hot tub is like a growling stomach waiting to be filled. How would you like it if you'd just dozed off after drying off early from life's trials and tribulations -- only to be awakened by the raucous, splashing sounds of revelry from yonder tub?