On the Waterfront : Sand from a construction site. Waves slapping--against cement. <i> Voila!</i> Malibu on New York shores.

There is something about people who live on the island of Manhattan that makes them refuse to accept limitations. No, it’s not too crowded; no, it’s not too dangerous. They are the type of Earth people who, if they were relocated to Mars, would insist on reproducing Times Square no matter how alien or hostile or impossible.

So it’s no surprise when people here strip to their bikinis, lather on suntan oil and settle down on sand with a bottled designer water on the spiritual equivalent of a construction site. Which they call a beach.

Manhattan has two such “beaches” amid the traffic and tar and noise.

There is a West Side (downscale) and an East Side (upscale) oasis of sand, sun, umbrellas, towels, volleyball nets and panoramic water views. There is no sea-foam-in-the-face but bathers can at least hear waves slapping--admittedly against cement, but it’s clearly slapping.

Don and Barbara Orlando are typical East Side beach-goers. In fact, you can’t get much more New York than the Orlandos. They’re 30-something residents of Bensonhurst in Brooklyn. They met in 1979 in the lobby of the Empire State Building. She worked there; he was in school.

Today, he is a hair colorist who drives a Mercedes; she’s a jewelry maker who pierced her bellybutton. Their Brooklyn-Manhattan passports will never expire because they really take advantage of the city: They do the theater, clubs, movies, restaurants, shopping, and last week they even took a mini-vacation in Manhattan, staying overnight at the St. Moritz after dinner at Tavern on the Green.

The next morning they wanted to work on their tans. Rather than go all the way to the “Island”--as in Long Island--they retrieved plastic beach chairs from the Mercedes trunk and sprawled out on the upscale floating beach in the East River at 34th Street.

The beach is actually an old barge covered with 200 tons of sand from--where else?--a New Jersey construction pit. No-body swims--in that water?--but “not a problem,” says Don in elegant Brooklynese. “We don’t do swimming. We do color.”

She read true crime; he read “Dino,” the unauthorized biography of Dean Martin. They wore bathing suits and sunglasses. They did not see anything incongruous in the phony plage .

“I don’t think this is so shocking,” Don screams above the thunder of a helicopter taking off at a nearby helipad. Although helicopters take off and land every few minutes, the noise doesn’t faze the Orlandos.

“We have a lot of fire engines by the house,” bellows Barbara. “So the helicopters . . . not a problem.”

Suddenly the “beach” starts to gently rock from the wake of a freighter gliding by. In a few minutes the place is bobbing. “I’m hating this,” says Barbara, raising an eyebrow. “I’m nauseous.”

But before they leave they must know about the 70-ish woman in the G-string leopard patterned bikini with a graying ponytail flopping atop her head. Everyone on the beach wants to know her story. (“What’s with Minnie Mouse?” “Who’s the old Kewpie Doll?”) But typically nobody talks to her. She opts out of an interview declaring in a slightly European accent, “I come to the sea to be alone.”

The sea?

This old woman in a thong bikini and tan from Ipanema is sitting on a rusted barge covered with sand. The view is of Queens. There’s no place to even get your feet wet. But she’s acting like this is the south of France?

There is no place like Manhattan to encourage such fantasies and nobody better to stoke them than Michael O’Keefe, who created the Beach Barge as a sideshow to his restaurant barge, The Water Club.

O’Keefe grew up in the shadow of the Throgs Neck Bridge and has spent his career as a restaurateur assisting New Yorkers to find food with salt in the air. Starting in 1984, he fought the city bureaucracy to be allowed to drag another barge into the East River as a stage for a beach.

Finally, 85 permits later, O’Keefe received permission this summer. While the beach is open to the public during the day, he uses it at night for private parties catered by the restaurant.

O’Keefe says if the bureaucrats would let him, he could build five more beaches in one weekend on abandoned piers and deserted stretches of Manhattan’s waterfront.

“Some elected official always says, ‘Great idea! Full speed ahead,’ but then it all gets bogged down by some commissioner who can’t even tell me who owns the land,” he says.

In fact, Manhattan’s waterfront, with the exception of a few parks, has been neglected by tangled city politics. There’s even a commission to figure out how to improve it, though almost nothing has been done for a decade, which is about how long the commission has existed.

The other “beach,” on the West Side, grew out of the imagination of an enterprising Israeli who was raised also on the water near Tel Aviv.

In 1990, Shimon Bokovza, 44, bid to take over one of many abandoned piers in the Hudson River in lower Manhattan. “Nobody else bid,” he says. “Only I wanted it.”

Trucking in 10,000 square feet of sand, cocktail tables with palm-thatched umbrellas and sculptures of jungle plants, Bokovza turned Pier 25 into Club Med-on-the-Hudson. He called it Amazon Village, though his business card refers to “TriBeCa Beach.” (There is also a Manhattan Beach, but it’s on the mainland, in Brooklyn. Go figure.)

In three years, Amazon Village became a hot spot in Manhattan’s club scene by night and a sort of Coney Island by day. There were bungee-jumping contests over the river. Water balloon fights at lunch. Tugs-of-war at sunset. Hula Hoop, body painting, competitive volleyball--all in full view of the World Trade Center and New Jersey.

But its popularity nearly killed Amazon Village last summer when neighbors from a high-rise across the West Side Highway complained to the community board and then the state liquor commission. Bokovza eventually lost his liquor license, which meant he could only serve at private parties.

Bokovza can’t pinpoint what bothered the neighbors so much. Perhaps it was the Tuesday night live shows with drag queens, classical ballerinas and fire eaters onstage simultaneously. “The shows got very weird,” he says smiling to himself.

On a hot August afternoon, the phone in Bokovza’s trailer-office rings every five minutes with New Yorkers asking if the beach is open today to the public. Sadly, he says no. He closed for the public because if he couldn’t sell beer it wasn’t profitable to run the beach.

Indeed, without people stretched out convincingly in swimsuits, TriBeCa Beach looks rather shabby, like a depressed and Prozaced Coney Island. Gone is the smell of barbecue and suntan oil. Oddly even the briny breeze seems stinky like garbage.

Still, Bokovza has had a total of 8,000 people at private parties this summer. He’s done a bar mitzvah, graduation parties and lots of corporate events.

“New Yorkers will do anything to be around sand and beer,” says Bokovza who also owns a restaurant in the Hamptons. “I’m gonna try to get back my liquor license so I can open up again to the public next summer.”

People like Bokovza and O’Keefe--not exactly Thomas Edisons perhaps but people who know what New Yorkers want--have always tried to make something more and something different in this city. In their cases, creating a little strip of Malibu on the hard and cynical shores of Manhattan seems to have freed people here to be the architects of their lives--and deny the reality of urban life.