DIANA NYAD comes down Wisconsin Avenue, not quite swaggering in her coarse linen suit and shiny Adidas, just giving notice right off she doesn't think of herself as one-shot media phenom. Those comparisons to Evel Knievel and his Snake River Canyon jump can go to hell, says a ladylike grin on her tomboy face.

The first talk show was at 8; this is her fourth interview today and it's not even mid-afternoon. Tonight the marathon swimmer will catch the shuttle back to New York, after which she'll promote herself and her new book in Cleveland, Chicago and Boston. The book is called "Other Shores" and it is the story of Diana Nyad's faststroking life. It was timed, of course, to coincide with her epic August swim - from Cuba to Key West which failed.

"Random House wanted me to go to 40 cities, all expenses paid," she says, talking in high, husky bursts. "I didn't want to go to any. We settled on six."

Welcome to the confusing world of hypeflop, where winning isn't everything and big-time failure can be a smashing success.

Not always. There is the memory of Jerry Ford's WIN button. And "Missouri Breaks." And a streak-and-poof Beatles hoax called Klaatu.

Hypeflop? Think of . . . Peter Bogdanovich's filmmaking career of late, of Tiny Tim, of Arnold Schwarzenegger, who was merely the best body builder in the world till a film called "Pumping Iron" and a New York PR wizard named Bobby Zarem pumped him into a beautiful person. For a season, anyway, Arnold Schwarzenegger was the toast of Elaine's.

Think of . . . practically every Super Bowl.

The Titanic.

Guru Maharaj JL.

Koreagate.

Punkrock.

Bruce Springsteen. (Loyalists would say he's still ascending.)

"Cleopatra."

"Exorcist II."

"King Kong" (Where have you gone, Jessica Lange?)

"Beacon Hill" (TV epic that wasn't.)

Thomas Dewey and the '48 election.

Perhaps you get the idea. Hypeflops come in all flavors. Size and quality never uniform, satisfaction not always guaranteed. Sometimes the hype takes time to flop; sometimes it doesn't. (In Webster's hype is a verb that means to stimulate and enliven artificially. A flop is defined as a fall. A hypeflop is not necessarily a failure; it is a fall from expectation.) Sometimes, who knows why, the hype doesn't flop. One thing is sure: We live now in the age of hype, the day of instant and shrill PR. That is not likely to change. Though there are a hundred overlapping factors in the hypeflop equation, a few can be singled out.

LEMON PRODUCT. As in comet Kohoutek, last seen 52 million miles from the sun and moving away briskly. "The Comet of the Century," the pundits at Time and nearly everywhere else thought in late December 1973.The QE-2, booked to the gunwales, sailed from New York on a three-day "Comet Cruise." Hypeflop.

Consider an odd, tartan-clad quintet out of Edinburgh, Scotland, who come hyped as the answer to the Beatles and aren't even sugary enough to be themselves. The Bay City Rollers. Today they're doing Saturday morning kiddie television - and still selling records.

Sid Bernstein, you might say, is responsible for the Bay City Rollers. He brought the Beatles to Shea Stadium in the '60s, and he brought the Rollers to Howard Cosell's TV variety hour (speaking of hypes that flopped) in 1975. Bernstein had seen the candy rockers in London and Glasgow and was "positive this could be marketed in America.

"I didn't say sustained."

Just thinking back gives Bernstein the bumps. "So I talked to Cosell. I told him this wasn't the Beatles, but a phenomenon unlike anything he'd seen since. I told him we should put the Rollers on his first show, have lots of screaming kids out front. Howard bought the concept. On a handshake. Then Roone (Arledge) bought it. Got it?"

Got it. The Rollers appeared on the flop-bound Cosell show on Sept. 24, 1975, in a remote from Europe. Two weeks later, they did the show live in New York. "I'm telling you," says Bernstein, "the kids were out there. Barricades were up. Cops were on horseback. It was Beatle time all over again."

But what happened? "Oh, later. I got you. Well, they couldn't play. You see, the bottom line is always product - talent and performance. I mean, once the exposure is there. . . ."

A change in tone: "Look, I'll level with you. I got these kids of my own at home. So I needed an act. I needed something exciting in my life. Got it?"

Got it.

BAD TIMING BASED ON PRECEDENT. Think of a car. Not just any car, but a long, low, streamlined car with "telematic" push-button transmission (imbedded in the steering wheel), wrap-around bumpers, concave side panels. Not to mention a chromed-up vertical grille that looks like somebody sucking a lemon. "A Ford sucking a lemon," is how the joke goes afterward.

The Edsel, of course.

"We survived," Guy T. Steuart II of Steuart Ford in Lanham said on the phone the other day with just a trace of remembered anger. Back then, in the fall of '57, Steuart was fresh from the army and had just joined the family business as manager of its spanking Edsel dealership in Silver Spring. When the cars arrived in Washington, they were hidden downtown, in the yards of the old Senate beer breweries; in the middle of the night Steuart trucked them out to Maryland.

"It was just the wrong car for the wrong time," he sighs. "What I learned is never, never again swallow anything whole."

Today, there are Edsel fan clubs and Edsel newsletters and Edsel conventions. You can hardly touch an extant Edsel. Sometimes Steuart sees one on the road and wonders if he could have it. He almost longs for one. Which only suggests the success of failure takes many turns.

BAD TIMING BASED ON PRODUCTION DELAY. Where is Tom Wolfe's long-awaited book on astronauts? And does anyone care about seeing "Apocalypse Now," after $30 million in production costs, 2 1/2 years of waiting, tiresome speculation in the trades? After this one Francis Ford Coppola could be Francis Ford Floppola. The backlash seems posed to strike. Anticlimax, some would call it.

Gay Talese has been promising his magnum opus on sex in America since 1971. An excerpt appeared in Esquire three years ago. That is dangerous.

Ditto Truman Capote and "Answered Prayers." Capote was prattling about his career novel as early as the October 1972 Esquire (where he "gave away" the opening sentence.) He is the author who once said on a talk show: "What I could do with a PR account hasn't been dreamed of."

OVERKILL. "The Great Gatsby". . . which Vogue proclaimed would dictate American fashion. "Two Lane Blacktop" . . . hyped on the cover of Esquire as the movie of the eon. Robert Coover's "The Public Burning." "Bluebird," that joint Soviet-American turkey with Elizabeth Taylor that opened with lavish ballyhoo at the Kennedy Center a few years ago. Has anybody thought of it since?

Consider a 34-year-old cocky, abrasive stuntman from Butte, Mont. The man is holding a press conference. He is going to jump a mile-deep Idaho canyon in his "sky cycle." In his fist is a check of $6 million (later admitted as part of the hype). "The greatest competitor in life is death," the man says with righteous bravery, conjuring his live gate, closed-circuit receipts, profits from Ideal Toy Corp.'s windup of himself. It is spring 1974. Evel Knievel's greatest hype has begun.

Modern hype didn't start with Evel Knievel; he just took it to new tawdry levels. His jump four years ago was a flop. His hype was a success. And the whole thing has since turned in on him. If Lindbergh's feat stands for a triumph of the human spirit, what does Evel Knievel's represent?

Lucky Lindy, boring through that dark dome of night 51 years ago, was the right kind of hyped hero, one guesses, for a complexity of reasons - timing and clean good looks not being the least. "Unsullied fame," President Calvin Coolidge called it afterward, pinning a medal on his chest. But also there was the quality of Lindbergh's challenge - not only the sheer odds of distance and duration, its epic scope - but the idea that he tried it alone. That is inspirational. The seeming impossibility of the act (one flashes to Hillary scaling Everest) is a kind of proof for the limitless potentiality of the human spirit. But most of all, he made it.

"Hype is never based on a real feeling for the product," says PR man Bobby Zarem. "I creates an ersatz feeling of success, that's all."

The temptation is always there. A few days ago Bobby Zarem sent out a mass mailing connected with his promotion of the film, "The Wiz," opening with great expectation. "The film is extraordinarily moving, fabulously alive, innovative and entertaining," Zarem's form letter said.

Earlier this year Zarem was featured in an ABC documentary titled "The Land of Hype and Glory." Zarem says he wonders now if the show didn't intend all along to be a slam at the publicity business. One segment featured the rock group, Kiss; some critics said that was a hype of a hype.

Somehow, overkill always seems to work for Muhammad Ali. Warren Beatty, too, though his product, most recently evidenced by "Heaven Can Wait," is usually first-rate. Beatty understands timing, too: He grants interviews sparsely.

Ali is the maestro of hype. Think of all those nameless palookas Ali has fought through the years, then remember him the night Sept. 15, a 36-year-old glistening phoenix standing in his corner 15 rounds later, brushing his hair, petting his face, mugging for the universe. That is hype-success.

Sometimes, overkill takes a double reverse - as in the recent Camp David summit. Half-way through, nearly everybody began saying the participants needed more flexibility, that things were grinding toward irresolution. The world seemed poised for the flop. Then, that Sunday night, presto! Deus ex Machinac hypeflop turned to hype-success. So who can predict?

FIELD-SHIFT. Bob Dylan, god of man and myth, makes a four-hour movie called "Renald and Clara." El Floppo. (His try at acting, in Sam Peckinpah's "Pat Garret & Billy the Kid," was largely panned, too.)

Norman Mailer, lion of literature, runs for mayor of New York.Nope, (And where is his giant novel?)

This past summer, ABC's "20-20" opens with a former magazine editor and the art critic of The New York Times as co-hosts. They get yanked the morning after the first show - instantaneous flop. Marshall McLuhanism come true.

Jim Brown ran for daylight in the NFL; as a movie star, he's third string. They say that, too, about Joe Namath, struggling now in a TV series. (An early motorcycle movie bombed.)

Jane Fona and Tom Hayden in politics. Henry Winkler in the movies: The list goes on. Moral? Change horses in mid-stream, and the world might not change with you.

'SON OF SYNDROME. "The Exorcist," everybody's scare movie, does $82 million in domestic film rentals; the sequel does $14. "Billy Jack" makes $32 million; the follow-up $6. "Summer of '42" earns $20 million; "Class of '44" $7.

And so on. There is an irresistible venal impulse in moviemakers and bookmakers and TV makers to follow a hit with a pale imitation. If one is good, why can't two be better? Except that it almost never works that way. "The Godfather," a godfather in the trend, did $80 million at a production cost of $6 million; "Godfather II," though a first-rate film, could only do $30 million. It cost $14 million to make.

Generally, say people in the movie industry, you can expect to reap 40 percent from a follow-up. That often isn't hay - though it's usually a surefire way to create a bomb.

GOING BIG LEAGUE. Two years ago Preston Jones, author of "A Texas Trilogy," was hyped on the cover of Saturday Review as the next Eugene O'Neill. Though the trilogy opened enthusiastically in Washington, and in fact continues to play successfully on a regional level across the country, it mostly flopped on Broadway, lasting just 61 performances. What happened? Hard to say, really. Was the show mediocre, after all - or was petty New York envy really at work?

Warner Wolf should have never left Washington. The boo of the week didn't work in the Big Apple.

So here now is 130-pound, shoulder-tapered, infectious-smiling Diana Nyad saying "No swimmer in the world could have done what I did. It was a 2,000 percent effort. It was as tough people wanted to be me. I was as tough as I wanted myself to be."

She says this over a gigantic coffee ice-cream sundae. For an hour she has been talking of life in the fast lane. She likes it. But she knows Andy Werhol's famous line about every American having 15 minutes in which to be famous.

"Look, a man came up to me on the squash courts yesterday and said, 'Diana, I just want to shake your hand. Congratulations.' He didn't say, 'Nice try.'"

No sense, then, of letting anyone down? "Who? Castro? Jimmy Carter?"

Something has flared in those intense eyes.

"If I'd gotten out of the water after 80 jellyfish stings . . . or when the delirium really hit . . . I mean, if the hero makes an effort nobody else could have made, then they love her for that. When I finished that swim, I had 2,000 telegrams waiting for me. How can that be failure?"

The answer is it isn't failure. In the best of worlds, Diana Nyad's try from Cuba to Florida last August wouldn't have been hyped at all. Effort would have somehow outed on its own, found its own reward. But that isn't the American way now. And so Diana Nyad, like the man who gave us pet rocks, like Sly Stallone and Linda Lovelace and so many others who have come and gone, runs and carries fire and doesn't fret about tomorrow. At least not much.

Futureflop. Who can say what hypes are out there now, burning to be known? Sid Bernstein, who brought us the Bay City Rollers, says he has something exciting in his life: A new act. Her name is Laura Branigan, and so far, swears Bernstein, she's mostly played rehearsal rooms.

She did do the Mike Douglas show, though. "Not since Barbara Streisand," Douglas supposedly said. "And I got Shirley MacLaine to look at her too. She said, 'Sid, I think you got one this time. Kid's got a voice like a beacon.'"

Laura Branigan opened recently at a New York club called Reno Sweeney's. There is no indication she is soon going to make the cover of Time. . . .