The copies were cheap. But that's what everybody wanted then: a cheap water bed. Within a year after Charlie Hall exhibited his prototype -- created for the living room and called "The Pleasure Pit" -- people started ripping it off.

Not that Hall probably minded much. It was 1968. The dawning of the Age of Aquarius. The afterglow of the Summer of Love. He was just a 24-year-old graduate student in design in San Francisco , living in the Haight like everybody else.

And people who wanted a piece of the water bed action could just hang out at Hall's Innerspace factory in Sausalito and figure out how to make them. Hey, no problem.

"There was one guy who used to come visit," says Hall. "He was a totally typical early water bed dealer -- he also sold orgy butter in the L.A. Free Press. He had a long criminal record. I never found out what his real name was until much later."

In 1971, Hall was awarded a patent for "liquid support for human bodies." He admits making very few attempts to enforce it. "These weren't respectable people," he says. "They just wanted to make quick money to start a dope farm in Oregon. It was hard to get them to respond to my requests for a license. The industry was too young."

Twenty years later -- just this week -- Charlie Hall has gone to court in San Francisco. It took him six years just to get a trial. He's suing Intex Plastics, a company that imports water beds from Taiwan, for patent infringement. He's seeking royalties, damages, whatever.

You may wonder why he'd still care. You may wonder why he'd bother suing anybody -- particularly now. Or why he'd go to the trouble of syndicating his lawsuit, raising $750,000 for lawyer's fees by selling stakes in the outcome.

You may think the water bed went away. You may believe it was replaced by the futon, the brass bed, the sleigh bed. You may believe it was just another horrible, laughable fad that deserves its two pages in the new "Encyclopedia of Bad Taste."

But you would be wrong.

Proof: In 1971, an estimated $13 million worth of water beds were sold. In 1989, the water bed industry took in $2.23 billion in retail sales -- including frames and heaters and water conditioners.

More proof: Today, nearly one of every five mattresses sold in the United States has got water in it.

It was the motion. The rolling, and the sloshing. It was supposed to repeat, or prolong, or exaggerate every move. And people were eager for new sensations. New sex. Zen sex and stoned sex and deeper sex and more sex.

"We never marketed it that way -- as a sex bed," says Hall. "But it was a bed that moved and people got erotic ideas. This was both good and bad."

By 1971, there were 7,500 water beds selling a month in Washington, even though they were banned by apartment managers. The Hecht Co. carried them in its "I Got to Be Me" shops and ran advertisements for "200 Gallons of Love." They "definitely" improved sexual activities, according to a water bed salesman interviewed in Arlington in 1972. Another salesman suggested that the water bed made sex between two people seem like three, "because the undulating mattress creates the impression that a third warm body is participating." Sensual and reportedly somniferous, the beds were immediately installed in area hotels and motels. Particularly the bridal suites.

Scary rumors were floated too, about seasickness, about floors collapsing under the weight (a king-size holds 260 gallons and weighs 2,300 pounds), about people being electrocuted in their sleep. The sheets never fit right. You bruised your legs on the frame. Worms were found floating around inside some of them, before dealers got hip to chemicals.

"I really wasn't a hippie," Hall says. "At the time, I very much wanted to invent a bed that would replace the innerspring mattress."

While "water beds" had been used in British hospitals for decades -- for patients with bedsores -- Hall says he didn't know anything about them. The Pleasure Pit he created for a class at San Francisco State was supposed to be a fluid "conversation pit" sort of thing. It was deep, square -- 8 by 8 feet. He had first tried a sack filled with Jell-O. Then a sack filled with liquid starch. Neither worked.

When the Pleasure Pit was exhibited in an art show at the Cannery in 1968, articles about the "Water Bed" appeared in newspapers across the country, even on the front page of the Miami Herald, Hall's hometown paper. "I learned," he says, "that August is a slow news month."

Lines formed outside the gallery, where the water bed was dimly lit in the back. It wouldn't really become commercial until a year later, when Hall started Innerspace. He made beds, delivered beds. And he was soon taking orders from a member of the Jefferson Airplane, one of the Smothers Brothers. Hugh Hefner wanted one for the Playboy Mansion.

"Sleeping on water is a very natural thing," says Hall. "You spend the first nine months of your life sleeping that way."

Hall's business went belly-up in 1975. By then, there were 32 Innerspace stores in California. The bed was regarded as top-of-the-line -- it didn't leak, it had a good heater, the sheets fit. Bel Air hippies and recently divorced doctors bought them. But how many of those were there?

"We were selling a first-class piece of furniture," says Hall. "We spent a million and a half in advertising, while the main consumers of water beds were college kids buying them from head shops. We were marketing for a mature buyer. It didn't work."

The slosh. The gurgle. These are now controlled. The mainstreaming of the water bed is so complete that there's even a mattress now called "The Superwaveless." There are water beds with adjustable waves for each side. And there are soft-sided water beds, without the clumsy frames.

"They look just like conventional mattresses," says Ray Delrich, executive director of the Waterbed Manufacturers Association. "So, when your mother comes to visit you, she doesn't say, Oh my God, my daughter's gone hippie!"

Water beds could still very well enhance sex, but aren't found under blacklight posters anymore, next to bongs or peacock feathers stuck in old Mateus bottles.

"Many of today's owners purchase flotation systems for not only the comfort, but for the back support and additional therapeutic benefits they provide," says Henry Robinson, spokesman for WH O, the Waterbed Health Organization.

There are headboards now. (Is there anything more respectable?) A variety of styles: "From traditional to fine woods, European lacquer finishes, modern Scandinavian," says Delrich. Both Sealy and Simmons offer water beds now -- or "flotation mattresses," as they've come to be called. And the therapeutic qualities of the bed are forever emphasized. Hospitals use them for patients with burns, bedsores, arthritis. In 1988, the American Journal of Diseases of Children published an article claiming that infants born to drug-addicted mothers did better if kept on small water beds rather than in bassinets.

And the Compton Fire Department in Southern California replaced all its regular mattresses with water beds last March to help with yet another survey of the bed's effect on back problems and sleeplessness.

"I could go on and describe this scientifically for 10 minutes," says Keith Koenig, owner of Waterbed City in Pompano Beach, Fla., "but sleep research studies show that water beds cut out tossing and turning by two-thirds."

There's a perception vs. reality problem, like those ads for Rolling Stone. According to surveys, most water bed owners aren't dirtbags or hippies after all. They're married. They own their own homes. They have children. Their average age is 32.4 years. Their average income is $40,000. They've had two years of college.

They live in the West.

There, the market penetration of the water bed is 23.1 percent. In the South, it's 12.5, mostly due to Florida. And in the Northeast, it's the lowest, at 8.1 percent.

The Waterbed Manufacturers Association believes the market could get a second wind, if only people knew the truth about water beds. The beds are now "virtually waveless," according to the WMA's Delrich. "And the baroque look is gone," he says. A new logo for the product has been designed -- like the wool label -- that includes the image of the moon, "the international symbol of sleep."

Meanwhile, could the water bed finally be dying? According to American Marketing Services:

1985: 4.2 million water beds sold.

1986: 4.0 million sold.

1987: 3.9 million sold.

1988: 3.8 million sold.

1989: 3.57 million sold.

Koenig has been selling water beds since 1971. Last year, sales at Waterbed City exceeded $34 million, but just six months ago, he broke down and sold his first regular mattress.

At water bed trade shows and conventions, Charlie Hall was always called "The Father of Our Industry." He was asked to give speeches. His face appeared on posters.

But when he began his patent infringement case against Intex Plastics in 1985, his friends at the WMA were distressed. They didn't believe his patent was valid, according to one source. They like to mention the "water-filled goatskins" the ancient Persians, or ancient Phoenicians or ancient Romans slept on.

The members of the WMA were also angered that they had invested time and money in the industry -- building it into a mature, respectable business -- only to have Hall turn up 15 years later, just as his patent was about to expire in 1988, and want a piece of it.

The WMA made several attempts to offer Hall a settlement, something to get him to stop the trial, which could disrupt the industry. Hall's investment partner, Roger Dillan, says the offers never exceeded six figures, and, well, Hall thought he deserved more. He was able to sell licenses to Sealy and Simmons, for a total of $200,000.

It was Dillan, a real estate investor and a longtime friend of Hall's, who came up with the idea of selling investment stakes in the case.

"It didn't seem unusual to me at the time," he says. "It's just the way I put together any boring real estate deal." And Dillan says he did it on principle. "I wasn't looking for opportunities for me, " he says, "and the other investors feel this way too. ... I actually felt sorry for him, you know what I mean. He's a very interesting human being, and a stereotypical inventor, heavily lopsided in being creative and technically inventive."

Being a heavily lopsided venture capitalist, Dillan raised $750,000 for Hall's legal fees by selling off investment units of $10,000. He sold mostly to friends, and his real estate clients in Marin County. He called the group of 32 investors WBX Partners. Later, in an attempt to avoid being accused of champerty, Hall signed over 65 percent of his patent rights to them. ("Champerty," a practice that is generally frowned upon, is an old English legal term for a situation in which somebody not naturally concerned in a lawsuit agrees to help defray the legal costs in exchange for a piece of the proceeds.)

Francis Utrecht, the attorney for Long Beach-based Intex Plastics, says he plans to challenge the lawsuit on the grounds that its unconventional financing is "against public policy," as he puts it. "Many states have champerty laws, although California doesn't. These prevent people from buying lawsuits -- simply gambling on them and then making a lot of money... .

"Aside from that, of course," says Utrecht, "we simply think the patent is invalid and not infringed -- because of earlier water beds. Water beds go back at least 100 to 150 years. Hall should never have received a patent for it."

Luckily for WBX Partners, there's some precedent for Hall's untraditional financing of his case. Gordon Gould, the inventor of the optical laser, sued laser manufacturers for patent infringement and won in 1988. Patent rights were sold in exchange for interest income -- a financial arrangement that went unchallenged in court.

And just last March, the most successful investor-financed suit in U.S. history ended. It was against the founder of Computer-Land, a retail chain. The investors' stake of 28 percent in the case won them -- 44 people in all -- $63 million. In 1981 they'd chipped in to raise $4 million, and are now seeing a payout of 16 times their original investment.

Between royalties and damages, Charlie Hall and WBX Partners could stand to be awarded as much as $100 million.

"That's a real optimistic figure," says Hall, "in light of the condition of the industry. Water beds -- all bedding, really -- is in a slump these days."

"If we saw $20- to $50 million of gross return," says Dillan, "I think we are in the range of what's realistically possible."

Charlie Hall isn't in desperate financial shape or anything. He lives in a ranch house in Northern California's wine country, with his second wife, Suzanne, and their 6-year-old daughter, Caroline. His 21-year-old daughter, Hilary, is a student at the University of California at Santa Barbara.

For 15 years, he's been the owner of Basic Designs Inc., and has been successfully selling his inventions for camping and sailing equipment -- most notably the solar-heated Sun Shower. "Actually," he says, "we've been sending lots of them to Saudi Arabia. The soldiers have been ordering them by mail." He's also developed a camping mattress that rolls up into a three-pound bedroll. "It equalizes the pressure points as you sleep," he says, "the same way a water bed does."

The water bed. He's still got some. Three at one house. Two at another. "Other people have made millions in the water bed business," he says, "but it's just been a pain to me."