The Pool on Seven Seas Explorer

You can be forgiven if you think that a 2,000-passenger cruise ship is "small." Relatively speaking, it is small when compared to the world's largest mega-ship, Royal Caribbean's Harmony of the Seas, which has a double-occupancy capacity of 5,479. In actuality, when people talk about "small-ship cruising," they are referring to an experience in a completely different class. The small-ship movement encompasses everything from a yacht with a few dozen passengers to a sailing ship designed for fewer than 100 people to larger yachts and ships that can accommodate several hundred passengers. When we talk about "small ships," we're talking about any ship that sails with fewer than 1,300 guests. For the sake of this discussion, we'll use the following classifications:

Small ships distinguish themselves from mainstream options in more ways than just physical size and passenger count. Luxury, personalized service and uncommon experiences are the overarching themes among the small-ship cruise lines. No matter how small the ship, you can expect more inclusive fares, interesting and unusual ports of call, high-end amenities, excellent cuisine and wine, and polished, personal service.

While large cruise ships have the real estate to offer cool amenities -- everything from water slides to ziplines and Broadway-style showstoppers in the theater -- small ships overcome their limited onboard attractions by positioning their diminutive size as an advantage. Fewer people means easier embarkation and an absence of queues. Friendships form quickly on a small ship, and the onboard camaraderie enhances the vacation. Smaller size means these ships can visit small harbors and sail shallow channels that traditional cruise ships can't squeeze into. They are also more likely to dock in the center of town, making independent exploration a breeze.

If small ships sound more appealing to you than their larger, floating-city-esque counterparts, choices abound. How do you know when small is too small -- or which small ships are still too big for your taste? We've broken down the small-ship world into four size groups, and will lay out the distinctions and appeal of each.

Read on to find out which size -- or sizes -- of ship will be your dream cruise.

Le Ponant at sunset

Small Yachts

The "small yacht" category includes ships that accommodate no more than 110 passengers. Here you'll find yachts that range in length from 120 to 360 feet, brought to you by Un-Cruise Adventures, Crystal Cruises and SeaDream Yacht Club. Compare that to Quantum of the Seas' length of 1,139 feet, and you see how much smaller and more intimate these yachts can be. Ponant's entry to this category is Le Ponant, a three-masted motor-yacht; a pair of windjammers from SeaCloud Cruises round out the list. You won't enjoy a voyage aboard a yacht in this category unless you love traveling with a very small group of people. If you wish to hobnob with a different group of people each night, look to a larger ship.

Small-ship cruising in general is all about the destination, and that's even more the case aboard small yachts. These downright tiny vessels can anchor in hidden-away bays and harbors, and can visit some truly off-the-grid destinations, such as Alaska's Kuiu Island or Curieuse in the Seychelles. Plus, small yachts put a premium on getting passengers close to amazing sites. For example, take Alaska's Inside Passage; while mainstream cruise ships sail past Dawes Glacier in Endicott Arm, yacht passengers don marine survival suits, board skiffs and get within feet of sweet seals sitting prettily atop icebergs floating in the strait.

Most port visits focus on the natural habitat or local culture of the destination, and many of these cruise lines hire well-educated naturalists and historians to interact with passengers each day, offering onboard lectures and leading shore excursions (which are included in the cruise fare in the case of Un-Cruise Adventures' trips). These experts are on hand to answer questions and provide a level of education about the region that makes the trip special.

One of the most appealing aspects of small yachts are their watersports platforms, which enable passengers to get right into the water rather than simply gazing at it from 10 decks up. All of the ships in this category, with the exception of SeaCloud's windjammers, have them. From the platform, you can go swimming or snorkeling right from the ship, or borrow a personal watercraft such as a kayak or canoe. SeaDream also has several JetSkis for passenger use. While some larger yachts and ships have similar onboard marinas, it's a different experience when you're sharing the facilities with so few people. It feels as if the yacht is yours alone, and you're simply enjoying the water with a handful of friends.

The onboard experience is also more like that of sailing on a private yacht. You'll get to know your fellow passengers -- who tend to be well off and well traveled -- and the crew will cater to your every need, quickly learning not just your name but your likes and your dislikes. The chef will incorporate locally sourced ingredients -- salmon in Alaska, pineapple in Hawaii -- at mealtime and can customize the menu to a certain degree for your personal tastes. On the flip side, choice will be limited to one dining venue (with breakfast and possibly lunch served as a buffet only) and a limited selection of dinner entrees (typically a meat, fish and vegetarian option). Though seating is open, mealtimes are set, but can change based on what's going on outside. For example, if there are whale sightings in Alaska, dinner could be delayed in order to allow everyone to get on deck and have a look.

Because the itinerary is so paramount on small yachts, daytime activities are pretty nonexistent. Passengers generally need to entertain themselves. While the sun decks are nice on all of these ships, only Crystal Esprit and SeaDream I and II have pools; the other ships only have on-deck hot tubs. The spa (if any) usually consists of one or two small treatment rooms. Some yachts do have a few fun high-tech toys -- like the submarine aboard Crystal Esprit or the golf simulator on SeaDream yachts. There are no theaters on these ships and the "casino" -- when there is one -- is often just one game table with a slot machine located in a nearby corner.

Cabins tend to be well-decorated but on the small side, and lack balconies or adjoining sitting rooms. Your stateroom will be well tended to and it will include amenities like luxurious linens and designer-brand bath products, but you'll likely want to spend more time out of your cabin than in it. SeaDream staterooms don't have balconies but the line came up with an interesting way to give passengers the opportunity to enjoy the sea air with its "sleep under the stars" program, where the crew makes up a Balinese bed on deck especially for you.

Wind Spirit

Large Yachts

"Large" yachts are those that accommodate between 140 and 400 passengers, and feel more like small-scale cruise ships than pumped-up private yachts. These capacities are ideal for travelers who want an intimate experience but prefer sailing with more than a few dozen other people. These ships are also a good bet if you don't like feeling the movement of the ocean; because they are larger, the ride is usually a bit smoother than small yacht options.

Large yachts in this category include Windstar Cruises' three motor-sail yachts and its three 212-passenger yachts; Pearl Mist from Pearl Seas Cruises; four mega-yachts from the French-flagged Ponant; Paul Gauguin's Paul Gauguin,which exclusively sails the South Pacific; three clipper ships from Star Clippers; and four ships from Silversea (Silver Cloud, Silver Wind, Silver Shadow and Silver Whisper).

There are some nice perks when you sail a large yacht. First of all, you'll have more choice when it comes to cabins. Some cabins on large yachts will have balconies with sweeping ocean views, while none of the ships in the "Small Yacht" category offer accommodations with verandas. Most of the ships in this category also offer a variety of suites that give you more square footage, space to dine in your cabin and outdoor furniture to enjoy on your veranda. Ships from Silversea offer butler service with every stateroom, which equates to an ultra-luxurious experience for all.

These larger ships offer more dining venues onboard. Silversea ships in this category, for example, offer three fine dining options -- The Restaurant main dining room, La Terrazza for authentic Italian flair, and specialty restaurant Le Champagne, featuring French cuisine -- in addition to the on-deck Pool Bar & Grill. Many lines -- including Windstar, Silversea and Paul Gauguin -- also stage elaborate BBQs on deck or on a beautiful stretch of beach.

The public areas of the ship offer more variety on a large yacht as well. You can expect amenities that could include at least two bars and even a standalone cigar lounge; a spa, beauty salon and full-fledged fitness center; a small theater; a casino; a library and internet/card room; and maybe even a small boutique selling clothing, jewelry and sundries.

Finally, these large yachts can visit some additional destinations that the small yachts can't visit safely (due to their size) but larger ships might be too big to access. Look for itineraries to the Arctic and Antarctica -- destinations that require larger ships with certain navigational equipment and strengthened hulls for sailing in areas where ice is prevalent. Large yachts also offer some compelling South Pacific itineraries.

Ultra-Small Ships

While previous ship size categories have been referred to as "yachts," the Ultra-Small Ship category covers larger vessels with capacities that range from 450 to 600 passengers, and all of these lines are positioned squarely in the luxury market. These offerings retain a sense of intimacy without being so large that you never fully learn the deck plan.

There are three 450-passenger ships from Seabourn on this list -- Odyssey, Quest and Sojourn -- and the line's new, 600-passenger flagship Encore will make its debut in December. While Regent has several ships in its fleet, only the smallest -- Seven Seas Navigator -- belongs in this category; the ship had a major refurbishment in spring 2016. Silversea's Art Deco-inspired Silver Spirit is another option and, in spring 2017, the line's new flagship Silver Muse will be another ultra-small ship.

This grouping consists of unique "boutique" cruise ships that all offer a high-end, all-inclusive experience with more amenities than those offered on yachts. All the ships in this range have open bars serving complimentary wines and spirits, and you'll have a choice of places to imbibe; for example, Seabourn's ships in this category have three lounges plus a pool bar. There's more choice of restaurants on ultra-small ships, when compared to the yachts, with main dining rooms, buffet venues and specialty restaurants. For example, all Seabourn ships are outfitted with The Grill by Thomas Keller, a chef whose three land-based restaurants are all Michelin-starred, in addition to the main dining room, casual venue, pool grill and room service. You'll also find communal gathering spots like Seabourn Square, Seabourn's take on an upscale coffee shop. Extra onboard pastimes -- such as mini-golf and shuffleboard (found aboard Regent Seven Seas Navigator) -- are also the norm on ultra-small ships.

Spa and fitness centers are expanded on ultra-small ships, and the sun decks are downright impressive, with larger pools, several hot tubs and outdoor grills and bars. Some even have on-deck jogging tracks. Daytime activities are plentiful, with more visiting lecturers and trivia as well as additional entertainment in the evenings, from shows in the theater to ballroom dancing in the lounge.

Like all small-ship cruise companies, those listed here offer itineraries around the globe with an emphasis on "greatest hits" destinations such as Barcelona, Venice and Athens, as well as more hard-to-reach or unusual ports of call like Croatia's Hvar or French Polynesia's Rangiroa. You'll also find longer voyages lasting 10 to 14 nights, as well as "grand voyages" that can keep you traveling for a month or longer.

The Lido Deck on Crystal Symphony

Small Ships

While the largest "small ships" on our list will never be in the league of behemoths like Royal Caribbean's Harmony of the Seas, they do cater to anywhere from 650 to 1,300 passengers. And while the onboard vibe is still intimate, you'll benefit from the larger size of the ships by way of additional dining venues, larger spas and pool decks, upgraded entertainment options like Broadway-style shows and multiple performers throughout the ship, more game options in the casino, and even extras such as standalone cooking schools.

In this category, we welcome the ships from Viking Ocean Cruises: the 930-passenger Viking Star and Viking Sea, and a third ship, Viking Sky, that will set sail in 2017. All of Oceania's ships -- Insignia, Nautica, Regatta, Sirena, Riviera and Marina -- fall into this grouping, as do both Azamara Club Cruises ships (Journey and Quest). Crystal's two traditional cruise ships -- Crystal Serenity and Crystal Symphony -- are small ships and most of Regent's Seven Seas fleet -- Seven Seas Explorer, Voyager and Mariner -- are in this category.

Each of these ships offers beautifully appointed cabins and suites, some of which offer access to a concierge or personal butler service. Expect a high level of service throughout these vessels, but high-end suites might come with additional perks like ensuite afternoon tea  or an invitation to dine with the officers. Of course, as the passenger count ticks up on these "larger" small ships, you might encounter a few downsides. The hot tubs get more traffic, so it's not so easy to get one to yourself. And it can be marginally more difficult to get to know fellow passengers; it's impossible to meet every single passenger on a ship with a capacity around 1,000 people.

These ships all tend to offer a plethora of itineraries that are longer in duration than seven nights. In the spirit of destination immersion, cruises include one or more overnights in popular ports and stay later than normal in other ports, so cruisers can see more on land and maybe even sample some of the destination's nightlife. These ships also visit more unusual ports than the mass-market lines and larger ships do, and those off-the-beaten-path spots often end up being the highlight of a voyage.

For foodies, some of these ships have super-special facilities. Take Oceania Marina and Riviera, for example. These O-class ships have the impressive Culinary Center that includes individual cooking stations for classes that will teach you everything from how to cook the perfect tomato sauce to how to design a meal around a series of tapas. Cooking classes aren't the only place where Oceania puts an emphasis on food. Its restaurants get high marks and some ships include an option from famed French chef Jacques Pepin. Viking Ocean Cruises also focuses on culinary immersion and offers its Kitchen Table, which is part shore excursion and part hands-on cooking experience. The day starts with a trip to a local market onshore with the ship's chef. Then, at dinnertime, you'll head to a test kitchen to help prepare a multicourse meal. This offering is limited to 12 people, so book early.

When a Small Ship Isn't the Best Choice

We've outlined the myriad ways in which small yachts and ships can offer amazing cruise vacations. However, small isn't always the right option. Families looking for dedicated kids clubs, character meet-and-greets and water parks and other amenities will be better off booking a high-end suite aboard a mass-market line that caters to all ages. Some of the mega-ships also have pretty spectacular VIP suites that include access to private sun decks/pools, lounges and restaurants. The "wow" factor on ships like that can be compelling. And, finally, mass-market lines definitely offer more itineraries that embark from easy-to-reach ports in the United States and beyond.