Today's buoyant cruise industry is churning out huge numbers of huge ships. Accommodations for 2,000 have become commonplace and, aboard a few giants, you will share your cruise with more than 3,000 fellow passengers.

When experienced cruisers hear these numbers, they roll their eyes and book elsewhere. But inexperienced newcomers don't seem to care. A ship, after all, is just a ship. Or is it?

Not really. Those distant white dream castles drifting across the sea may seem interchangeable, merely glittering conveyances dedicated to seagoing luxury and delight. But the size of a vessel is crucial, determining the nature of the on-board experience. Yacht-like miniatures offer an ambience that stands in sharp contrast to life aboard towering leviathans.

Megaships offer a range of amenities undreamed of aboard smaller vessels: Elaborate show lounges, Broadway-style entertainment, Vegas-style casinos, generous dining alternatives, veritable shopping malls, an upper deck sun bowl with a choice of swimming pools, miniature golf courses and paddle-tennis courts, acres of teak for secluded sunbathing and elaborate health spas rivaling anything ashore.

And then there's a sense -- perhaps most seductive --that you have embarked within a happening, seagoing city; a feeling reinforced by the naval architecture that comes with the territory -- a towering atrium with lagoons, waterfalls and palm trees. (And an average per diem of $200.)

Recent United States demographics may offer a clue to the megaships' popularity. Americans have increasingly abandoned rural isolation, migrating inexorably toward cities. It is no wonder, then, that when going to sea, many might feel a compunction to embark on a ship that seems irrefutably urban.

So if megaships are floating cities, then miniships are floating villages. For our purposes, I shall ignore those small ships undertaking what are called adventure cruises, dwelling instead on high-end luxury vessels, on which the per diem averages $500 to $600.

This luxury market provides different attractions to a very different clientele. Booked aboard these rarefied small ships, you will find traditionalist holdouts who, despairing of passenger-loads in the thousands, opt for passenger-loads in the low -- very low -- hundreds.

They can choose from an intriguing flotilla. Smallest of all are three ships of Renaissance Cruises -- Ren 6, Ren 7 and Ren 8 -- which can embark no more than 114 passengers each. Marginally bigger are two Sea Goddess vessels, originally Norwegian but now flying Cunard's house flag. Sea Goddess I and II each has cabins for 116 passengers. Appropriately, both cruise lines define their ships as yachts.

A small-capacity step upward is a quartet of Windstar vessels sailing cruise ships that admit 148 passengers. Three elegant Seabourn Cruises vessels, whose owners prefer the appellation "cruise ship" rather than yacht, carry 212. Slightly larger are two from Silversea Cruises that retain their small-ship ambience even though they can pamper 296 on board. Radisson Seven Seas Cruises has a disparate fleet that includes 350-passenger Radisson Diamond, 180-passenger Song of Flower and brand-new Paul Gauguin, accommodating 320.

Small ships, older passengers

On small ships you'll generally find advanced passenger age, low density, high per diems, exotic itineraries, lavish cabins, open sitting, mostly free drinks, no tipping, open bridges and what interlopers from big ships might perceive as nothing to do. But that is precisely what small-ship passengers crave: doing nothing, or perhaps more accurately, not being expected to do anything.

Of course, those upscale passengers do read, gossip, snooze, swim, sun, dance, eat (extremely well) and rub bronzed, companionable shoulders with celebrated VIP-lecturers brought on board to stimulate the mind. But they dislike regimentation, loathe crowds and can enjoy their languid, seagoing routine without recourse to napkin-folding demonstrations, pool games, art auctions or grandma brag parties (although there are plenty of grandmas aboard, if very few grandchildren). In socio-maritime terms, within these select floating hamlets, less is most definitely more.

Small-shipboard life is serene and self-contained, the pace deliberately slowed and activities kept to a minimum. Architecturally, smallness works wonders. Everything is close at hand, the commute between cabin and pool or dining room minimal. The on-board decor tends to quiet good taste, service is silky smooth and, despite modest entertainment (nothing to rival big-ship extravaganzas), evenings by and large are dedicated to conversation and the palate.

Also on a small ship, people tend to know everyone by cruise's end because they dine with a different group each evening. Separate sittings do not arbitrarily divide the passenger-load in half as on big ships. I often think that passengers aboard small ships are more like fellow members of the same club.

However much I relish passage aboard those little ships, I remain at the same time a stubbornly urban creature. I grew up in London and remain today an incurable New Yorker. So these new big ships don't intimidate me, they intrigue me.

As a dedicated passenger and maritime historian, I am fascinated by the differing ways that mega-ships absorb their megapopulations. The impact of all those fellow passengers embarked within vast hulls depends very much on the ingenuity of the naval architects.

Pursuit of intimacy

Throughout Carnival's and Royal Caribbean's megaship fleets, there seems no collective mea culpa, no apparent apologia about their vessels' daunting capacity. What you see is what you get. But aboard Princess' larger ships, there is a concerted -- and successful -- effort to reduce the impact of the numbers.

Contrast dining venues aboard Royal Caribbean's Legend of the Seas and Sun Princess, both with a passenger capacity of approximately 2,300. On the former, one enters a vast, double-decked chamber lined with tall windows to either side. This expanse of glass gives every table a view of Alaskan mountains by day, but at night, even decorative, motorized shades cannot diminish the space's overscale void in which you are breaking bread with a thousand people.

But aboard Sun Princess, designers rejected the temptation of a huge dining hangar in favor of two, single-decked smaller rooms, dividing each sitting in half. In pursuit of further intimacy, each of these modest rooms has been purposely and cunningly subdivided. Throughout the center of the room, curving wooden and glass baffles enclose small groups of tables; and from each side of the hull, partitions extend inboard to further interrupt the space. As a result, the apparent size of the dining room is drastically reduced. There may be 600 at table, but the perceived capacity from every passenger chair seems refreshingly less.

For those dismayed by dizzying passenger numbers or per diems of the upscale miniatures, there are still some intermediate-sized hulls available, neither mega- nor mini-, but metaships. Within the range of 600 to 1,200 passengers, try Marco Polo, Stella Solaris, Royal Princess, Island Princess, Vistafjord or even the twinned luxe of Crystal Harmony or Crystal Symphony. These midsized cruise ships, ground between neither millstones of leviathan nor yacht, seem an endangered species, despite the fact that three decades ago, this was the size to which every vessel aspired.

Though metaships are deemed insufficiently profitable, it is heartening to read about projected midsized newbuildings: Royal Olympic has ordered two, possibly three, 800-passenger ships and Renaissance Cruises has a quartet of 685-passenger vessels under construction in France. They will be called, cryptically, R-1, R-2, R-3 and R-4 -- sounds like a destroyer flotilla.

Quest for capacity

Still, ships are getting bigger because cruising is so popular. Americans and, increasingly, Europeans and Asians, are hooked on shipboard life, fueling a seemingly insatiable demand for more berths. Equally important, big ships are in vogue because of an inescapable shipping principle called Economy of Scale, a term that I feel demands capitalization because of its significance throughout the industry.

Economy of Scale means that it costs cruise lines less to book a horde in one big hull than to split the same horde in half in two small hulls. Every passenger vessel, regardless of size, requires a captain, a cruise director, a chief engineer, a maitre d'hotel, etc., all of whom are paid the same regardless of the vessel's size. This principle holds true even though megaships require a vastly larger staff of dining room, deck and cabin stewards whose wages are offset by a proportionally larger passenger load. So the more passengers on board one vessel, the better the manpower bargain for the company.

Companies are gunning for, if only temporarily, the world's largest passenger ship. Two years ago, 100,000-ton Carnival Destiny, with identical Triumph and Victory to follow, was the first to break through the six-figure displacement ceiling. Then Grand Princess entered Mediterranean service this past May, weighing in at 109,000 tons. Once again, two more will follow (Grander and Grandest?). But wait: Not to be outclassed in the megaship stakes, Royal Caribbean International is building a pair of 142,000-ton monsters in Finland.

There are no simple answers to how many people these immense vessels embark because megaship owners tend to volunteer two different figures, one proudly, the other reluctantly: Double occupancy as opposed to maximum occupancy. The first counts noses with only two inhabiting every cabin, the second takes into account cabins with third or fourth berths as well.

Don't hype the size

For example, double occupancy aboard Carnival Destiny is 2,642, but maximum occupancy jumps to 3,400. Grand Princess welcomes aboard 3,100 maximum occupancy, but prefers advertising their double occupancy head count of 2,600. Royal Caribbean's two behemoths will each absorb 3,100 double occupancy but a whopping 3,840 when every berth is filled.

I can only guess that cruise lines prefer the lower figure because it conveys the impression that their ships are smaller. Here's a fine megaship paradox -- order ships of record-breaking size, but soft-pedal their record-breaking capacity. In other words, don't put off prospective clients by making them feel that they will be lost within a teeming onboard population. Whereas "a cast of thousands" is an acceptable publicity come-on, "a passenger-load of thousands" is patently not.

I am not convinced that this curious, head-in-the-sand attitude makes sense. Ever since the debut of the North Atlantic's first grand ship -- the Great Eastern, an over-hyped white elephant from 1861, as well as the poor doomed Titanic of 1912 -- the seagoing public has always been attracted to big ships, the bigger the better. And today, that historic fixation seems eminently justified.

But size notwithstanding, cruise ships and cruising are delightful. If you can cope with the numbers, clamber aboard a giant; if not, try one of the yachts.

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