At the height of the Virginia Beach tourist season, hotel manager Skip Hendrix starts looking for the man from Quebec. He generally arrives in mid-July, at about nine in the morning, having driven 750 miles with his wife and kids. He always wants to stay for two weeks. And he never phones ahead.

"He's been coming for five years without a reservation," says Hendrix, whose Schooner Motor Lodge fronts the Atlantic Ocean. "We always find him a room, even if we have to put him in three or four different rooms for a two- week stay. When he leaves, we always say, 'It was nice to have you back. Here, take one of our brochures and call us next time.' But he never does. I guess it's his spirit of adventure."

The hotel folk don't advise it -- and there's always some risk -- but you, too, can sneak to the beach and find a place to stay.

At Virginia Beach, about four hours' drive from Washington and an easy jaunt by jet, the chances are good, even on a warm weekend, if you come early enough in the day. But if you venture north to Maryland and Delaware for the 28-mile stretch from Ocean City to Rehoboth, the odds are somewhat dicier.

Sue Stone of the Rehoboth Beach Chamber of Commerce, for one, counsels against the practice -- though you can always try sleeping illegally in your car, she agrees. "You're pretty much guaranteed a place to stay then," she quips -- that is, a jail cell as your last beach resort.

Arriving unprepared is "a scary thing to do," Stone allows -- and horror stories abound. Early one morning a few summers ago, the Haynali family of Prince George's County landed in Ocean City to hunt a berth for the night. Of the few motels with empty rooms, all insisted on a two- night minimum. After scouring the coastline from Maryland to Delaware, the Haynalis finally decided to accept the condition, though they still planned to stay just a night. But by then the whole peninsula was solidly booked. They returned to Prince George's frazzled and pale.

Few things can be more exhilarating, however, than grappling with and triumphing over the great unknown. "I myself like to take my family down to Cape Hatteras or Nag's Head," says Hendrix, the Virginia Beach innkeeper. "Sometimes I make reservations. Sometimes I don't."

The other day, we conducted an informal experiment on the shifting sands of the last-minute beach. As Memorial Day Weekend got under way, and summer suddenly became more than an interesting proposition, we dispatched two travelers incognito. One headed south and the other north on a quest for bed and board without bedding down on the boardwalk.

There was only one restraint -- no reservations for rooms. Virginia Beach has 6,500, while the Delmarva Peninsula boasts 9,000.

Here's what they found:

A lot of sand. An ocean still too chilly for all but the hardiest hydrophiles. Dolphins, frolicking just off the Virginia shore most mornings after dawn.

High-dollar restaurants, with the 1978 Chateau Laffite Rothschild at Virginia Beach's Captain's Table listing for $175 a bottle. A motherlode of miniature golf. The Solidor: "a heavy, hulking alien covered with fur, with dark, deeply hooded eyes above sharp, lethal teeth." Not encountered kicking sand in people's faces, but at Virginia Beach's Royal London Wax Museum.

New trends: foldover sunglasses and magic water snakes in the tourist shops at Delmarva; a substantial increase in the number of "ALL U CAN EAT" signs -- or "Stuffa You Selfa," as Giovanni's Pasta Pizza Palace has it -- at Virginia Beach; hot tubs in your room, $160 a night at Virginia Beach's newest establishment, the swingingly single Crosswinds. Not a hula hoop in sight.

And room rates that rise and fall with the logic of porkbelly futures.

The Virginia Beach correspondent reached his destination shortly before six on Friday evening in the thick of inbound traffic, having already reaped an unexpected reward from doing things at the last minute.

As he discovered on arriving late at National Airport, USAir had oversold its flight to Norfolk, a half-hour drive from the surf, and wouldn't let him board the plane. Instead the airline found him a flight to Newport News, paid for a limousine to Norfolk and further favored him with a free roundtrip ticket anywhere. He's considering San Francisco. But back to the beach.

The first place he tried was the Aquarius, a white concrete apparition towering over Atlantic Avenue at 19th Street. The clerk said he could stay for $88 a night in a two-room apartment sporting private terrace and kitchen. "They're all exactly alike. They all face the ocean. We'll be full-up by tonight," he said grimly.

The traveler pressed northward to the Greenwood, a wood-frame ramshackle affair a few doors up the ocean front. There was one room available for $56, and a smaller one free the next night for $36. "You better decide soon," said the gent behind the desk, urgently tapping his wristwatch. It was 6:05.

Next was La Playa, fronting the water at 33rd Street. There was a $75 room, more or less overlooking the waves, with a two-night minimum. "You can't stay just a night. Everybody in the hotel-motel association is supposed to require at least a two-night minimum," asserted the woman on duty. Told that the Greenwood, for one, was offering a room for a single night, her gaze sharpened suddenly with interest. "Thanks for the info," she said, adding the by- now familiar warning about time running out.

At about 6:30, the desk clerk at the leviathan Sheraton Beach Inn, straddling 36th Street like a great blue whale, offered a host of empty rooms, ranging from $79 to $90 a night. The most expensive boasted a view of the ocean; the cheapest was convenient to the icemaker.

Shortly before seven, the visitor settled on Oceans II, a low, terraced building at 42nd Street, near the edge of the resort strip and past, as it happened, a dozen "VACANCY" signs. An ocean-view efficiency with kitchen and Murphy bed was going for $40 a night. The traveler paid for two nights in advance.

Here was a place ready-made for the last-minute traveler. A motel gone condo, Oceans II often plays host to its individual owners, while rooms for non-owners are catch as catch can. "About 70 percent of our business is off the street," said the clerk. It was, in any case, among the best buys on the water.

The northbound correspondent checked his brains at the Bay Bridge, as the old saying goes. That is, he went by car. With stops along the way -- one to leave a pesky dog with relatives -- it took six hours to forge to Rehoboth. He made his destination by nine at night, finding scant parking on the main drag, and an air of festive frenzy on the sidewalk. Lots of people promenading, celebrating summer.

There were also, at this late hour, plenty of vacancy signs. Beat 'em down, he thought with confidence. Look for a deal.

On the land side of Baltimore Avenue, the Admiral Motel had $48 rooms for a single night. But if you wanted to stay longer, the price was $69 a night. "That's just the way it is," the clerk said with a grin.

On the ocean side, the Atlantic Sands offered rooms for three nights only, at $67 per. Less sanguine about a bargain, the adventurer tried the Sirocco, which had ocean- front units at $69 a night, with advance payment-in-full required. "No money, no reservations," said owner Edna Destino. It was now after 10 o'clock.

The Commodore, a brand-new palace on Rehoboth Avenue, was selling rooms at $69 -- promptly revised to $59, after a little prodding -- while pushing a long-weekend package featuring a late checkout on Monday. "Only $200," the night clerk ventured. He didn't seem to be joking. It was approaching 11 o'clock.

Down the block on Second Street, the Oceanus ($59 a night) had the heat going full-blast. "Doesn't it need to be?" shrugged clerk Jim Smith. "I wouldn't take a chance on not getting reservations," Smith said under cross- examination. "I've tried too many times to find people rooms."

In Dewey Beach, a mile away, the visitor hit beach blanket bingo: the Royal Surf on the water, at $48 for Friday only, featured free beer, fruit juices, popcorn and morning coffee. It was booked for Saturday and Sunday, though. He checked in anyway.

On Saturday, he moved across the street to the Adams Ocean Front Motel, with its two-night package for $100 plus tax -- ice, doughnuts and hot coffee included in the price.

For most of the weekend it rained.