Before the jet age, when ocean liners were built to cross seas, not cruise them, passengers would sit in wooden deck chairs and promenade the long teak decks to exult in the grandeur of the world's biggest landscape.

Now it's the ships that are breathtakingly big. And while cruise companies defend the bigness - "Our ships still look like ships," said Julianne Chase, a spokeswoman for the Holland America Line - it seems that the ocean is getting eclipsed.By the year 2000, new cruise ships will be carrying as many as 3,000 passengers, said Steven Gordon, publisher of Star Service, a travel industry guide, adding that just a few years ago, 800 seemed big (the Titanic only carried 2,200). "You can't put 3,000 deck chairs out," he said.

Peter McMullin, a cruise industry expert and a founder of Southeast Research Partners in Boca Raton, Fla., said, "Ships are getting larger - they're like floating hotels."

Richard Sasso, president of Celebrity Cruises, calls them "floating cities." Celebrity has launched three in the last three years, including the 1,870-passenger Mercury in October.

Travel experts say cruising is more popular than ever, with movies like "Titanic," oddly enough, attracting younger passengers. But unlike the old liners, new pleasure ships, built to hop from port to port, are packed with air-conditioned amenities that make the out-of-doors seem beside the point.

The focus has moved indoors to spas, lounges, lobbies, casinos, theaters and much grander cabins. "You're never sure whether you're in a Liberace casino, a cucaracha lounge, or the Peachtree Center in Atlanta," said the architect Lee Mindel, who designed some of the Mercury's interiors.

Whatever happened to the water?

When Celebrity Cruises (now owned by the Royal Caribbean line) asked Mindel and Peter Shelton, of Shelton, Mindel & Associates in New York, to design the main dining room and other public spaces on the Mercury, the architects had one priority: to remind passengers they are really at sea. But the spaces had to be snappy enough to wow the regulars and strong enough to hold up against glitzy rooms designed by other noted firms - including Birch Coffey Design Associates of New York - that had been hired to make the Mercury what Sasso calls a "five-star, upscale, premium product."

In addition, Shelton, Mindel had to figure out how to maintain the firm's own standards for warm and elegant modernism. "Simplicity is probably the most complex thing to execute," Mindel said.

Le Corbusier, in his 1923 primer, "Towards a New Architecture," rhapsodized about the natural modernism found in ships, citing as an example the teak-and-steel promenade deck of the Empress of France: "An architecture pure, clear, clean, neat and healthy," he called it, unfettered as it was by "carpets, cushions, canopies, wallpapers" and other comforts then in favor with modernism's opponents.

But in the "feeding frenzy of accouterments," as Mindel describes cruise ship design, Le Corbusier's ascetic is not easy to pull off. Initially, Celebrity Cruises "wanted to soup things up, add more embellishments, put shoulder pads on everything," Mindel said. To win them over, he and his partner made a computerized movie in addition to the usual drawings to show just how dynamic their elegant design would look in reality.

Eating is the main activity on a cruise ship - and Shelton, Mindel designed the Mercury's main dining room, the Manhattan Restaurant. Demetrios Kaparis, the naval architect, had put the dining room at very back of the ship, instead of in the usual midships location, and had squared off the stern in a two-story picture window - a feature Kaparis says is unique to Celebrity ships - three of them have it.

"With the aft sheared off, you see the wake of the ship trailing behind you, the thrust of the water, and begin to feel the power of the movement," Mindel said. "The view is panoramic, almost cinematic, and that's what started to generate our design." The problem was the view at night, when the sea turns black and the big picture window becomes a mirror. So for evening, the architects ordered up photo murals of the Flatiron Building by Michael Moran. They slide from the ceiling like stage flats for a big Manhattan musical.

The double-height space feels urbane. Tall, timberlike columns wrapped in teak-stained cherry flank a long, sleek staircase railed with stainless steel. Overhead looms a giant steel chandelier inspired by one designed for the Empire State Building.

The architects also gave the dining room a 1930s-inspired wool carpet on which abstract flocks of birds seem to be soaring over a deep blue sea. "We wanted it to look as if Cubist gulls were following the wake of the ship," Mindel said.

A bold interior was necessary to absorb the bright daytime glare. "Inside, you need a strong palette of clear, bright colors," Mindel said. So the architects chose a mix of red, white and deep blue "They are nationalist colors," he said, adding they evoke "great institutions and great ships like the Ile-de-France and the Queen Mary."

The architects designed two other public spaces, Rendez-Vous Square and the Aft Atrium.