The majority of cruise ships out there are huge, bustling affairs that sail 7-night (or shorter) cruises to warm weather destinations. Plenty of people love the buzz of big. But if the idea of being at sea appeals to you, but not on an airplane-hangar sized ship with 3,000 others, don't give up hope. There are small and medium-sized ships out there as well.

Read on to explore the difference size makes.

Megaships (1,800¿3,600+ passengers)

Americans are obsessed with big. From the SUVs many of us insist on driving, to the mansionettes we build and the refrigerator-sized packs of toilet paper we lug home from Costco. So, it's no surprise many of us like our cruise ships big too. So much so, that the cruise lines continue to push the limits of size, one-upping each other at every turn. Currently, the QM2 is the largest and longest ship, at 151,400 tons and 1,132 feet long, and carrying 2,620 passengers double occupancy. In April, Royal Caribbean's Freedom of the Seas will debut and snatch the title of largest cruise ship at 160,000 tons with a capacity of 3,600 passengers double occupancy (though 20 feet shorter than the QM2).

Just when you thought things couldn't get any bigger, a few weeks ago Royal Caribbean announces its intention to build an even more gigantic class of ship, the 220,000-ton, 5,400-passenger Genesis class. Yikes!

Moving away from the upper upper end of the size spectrum, there are dozens of ships that range in size from 70,000 to 140,000 tons and though surely considered "mega" ships, carry a mere 2,000 to 3,000 passengers.

All of these huge-o ships offer an onboard experience any city-slicker will recognize: food and drink available at any hour, entertainment districts filled with neon and twinkling lights, monumental architecture, big crowds, and a definite buzz. You often won't see the same faces twice from day to day, and, in fact, if you don't plan specific times and places to meet up with your cabin mates, you'll likely roam the decks for hours looking for them. (Some passengers even bring a set of walkie-talkies to stay in touch -- as annoying as they are to the rest of us.) The megas have as many as 12 or 14 passenger decks filled with shops, restaurants, bars, and lounges, plus cabins of all shapes and sizes. Most have a grand multistory atrium lobby, three or four swimming pools and hot tubs, theaters, a pizzeria, a specialty coffee shop, and one or more reservations-only restaurants. Mammoth spas and gyms boast dozens of exercise machines and treatment rooms, and vast children's areas include splash pools, playrooms, and video arcades. Countless activities are offered all day long, including dance lessons, wine tastings, fashion shows, art auctions, aerobics classes, bingo, bridge, cooking demonstrations, pool games, computer classes, and trivia contests. And at night you have a choice of piano bars, discos, martini and champagne bars, sports bars, casinos, theaters, and show lounges.

As similar as they are, the megas have their particular quirks and qualities too. Carnival and Costa's ships are the most theme-park-like, with their over-the-top decor and ambience. Royal Caribbean's and NCL's megas (especially their newer ships) are more like Times Square hotels, blending a lot of flash with some elegant areas. Princess goes for a sort of Pottery Barn design sense and fun but not-too-daring activities and shows, and Holland America's and Disney's megas blend tradition with some bright, modern spaces, with Disney, of course, catering to families and HAL, more to middle aged (and older) couples. Celebrity is king in terms of sleek modern decor and a near-upscale ambience.

As a general rule, these ships are so large that they're limited as to where they can go. Ships in the 100,000-ton range are too big to fit through the Panama Canal, and so operate from the same coast year-round -- West Coast ships doing Mexico itineraries in winter and Alaska in summer, say; East Coast ships either staying in the Caribbean year-round or spending the summers sailing in Europe or New England/Canada. Some ports also lack docking facilities to accommodate these huge ships, meaning you either won't visit them at all or you'll have to be tendered ashore in shuttle boats, which generally means more waiting in line.

Midsize Ships (600¿1,800 Passengers)

We middle-of-the-road types appreciate the mid-size ships, which are, of course, smaller than the megas and bigger than the smallest.

Are you still following?

The term midsize is, of course, relative. Measuring in at between 20,000 and 60,000 gross tons, most of these ships are still larger than some of the great old ocean liners. Titanic, for instance, was only 46,000 tons. They're plenty big and spacious enough to provide a diverse cruise experience, though you won't find quite the ice-skating rinks, climbing walls, miniature golf, water slides and number of restaurants you do on the megaships. Consider that a good thing: For some people, a more toned-down, lower-key cruise is just what the doctor ordered, and further, many of the mid-sized ships offer quite impressive enrichment programs with lecturers and classes schedule throughout the week. Most of Holland America's fleet fits that description, aside from its mega-size Vista-class ships. MSC Cruises operates a pair of 58,600-ton, 1,590-passengers vessels and is really embracing the midsize zeitgeist in their onboard programming. Oceania Cruises operates three even smaller vessels, carrying only 684 passengers apiece in a country-club type setting. NCL also still offers a couple of midsizers, though they're the older ships in their fleet and are already on the chopping block. (All will have left the fleet by 2009.)

Among the true ultra-luxury lines, midsize is about as big as it gets excluding Cunard's megaliners. Crystal and Regent Seven Seas both operate ships in the 50,000-ton range, carrying 700 to 940 passengers -- a telling figure when you consider that MSC and NCL's similarly sized ships pack in twice as many passengers. Along with high-toned service, cuisine, and amenities, personal space is a major difference between the mainstream and luxe lines.

Small Ships (12¿450 Passengers)

If the thought of sailing with thousands of other people makes you want to jump overboard, but yet you do like the idea of a cruise, a smaller ship may be the answer. Small ships are ideal for those who crave a calm, intimate experience where conversation is king. As in a small town, you'll quickly get to know your neighbors, since you'll see the same faces at meals and on deck throughout the week.

There is a great range of small-ship styles, including sailing ships, coastal and river cruisers, expedition ships, and small luxury ships.

Sailing ships have sails, of course. And some are relied upon more than others to actually propel the ship. On Maine's coast, the 14 independently owned ships of the Maine Windjammer Association are bona fide sail-powered vessels, most without engines of any kind. If the wind stops blowing, get out the ores. Their only option is to let down their motorized yawl boat and try to push the ship into wind. The ships of Windjammer Barefoot Cruises, Star Clippers, and Windstar, on the other hand, usually operate under wind power for a part of each cruise---enough to create the sailing ambience---but they have engines to do most of the pushing. All these vessels tend to attract as many passengers in their 30s as in their 70s, all of them looking for something a little different than a regular cruise.

Coastal and river cruisers, on the other hand, are small vessels designed to sail in protected coastal waters and rivers. Very casual (and for the most part relatively plain), these ships offer a cruise oriented heavily toward nature, wildlife watching, culture, and history, with onboard naturalists to help interpret what you see. In addition to coastal cruisers, Cruise West, Lindblad Expeditions and Clipper Cruises also operate tougher expedition ships able to sail in the open ocean. Rounding out the small-ship options are the nostalgic Mark Twain¿style stern-wheelers of Delta Queen and American West, which turn the clock back on trips along the Mississippi, the Pacific Northwest's Columbia and Snake rivers, and Alaska's Inside Passage.

The small luxury ships of high-end lines such as Seabourn, Silversea, and SeaDream offer a refined, ultra elegant ambience. Cabins are spacious, gracious waiters serve gourmet meals on fine china, and guests dress to impress. These ships also offer few activities besides watersports, putting more emphasis on low-key relaxation and high-end ports, such as St. Barts and Monte Carlo. American Safari Cruises operates truly tiny yachts carrying only 12 and 22 passengers. Service-oriented like the luxe ships, they also offer an adventure-travel vibe, with lots of built-in active excursions.

So, before you assume all cruises are like, think again. Size really does matter.

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