Several new cruise ships are hitting the high seas this year, including Royal Caribbean's Harmony of the Seas, which made its inaugural sailing last month. With a 6,780-guest capacity, Harmony reigns as the world's largest cruise ship, and is the third Royal Caribbean ship in the past six years to claim this title.

Still, the cruise line's executives insist they didn't set out to break any records when they started to work on Harmony.

"It doesn't enter into our decision-making," says Royal Caribbean International CEO Michael Bayley. "It's great to be able to say it's the biggest ship in the world … But we don't design that way."

Instead, Bayley says his team first decided what to include on the ship and then figured out how big it needed to be to fit innovative features and amenities.

"We literally spent the next few years moving things around, trying to figure out how we can get all of this to glue together," he says. "Then, bingo – all of a sudden, Harri [Kulovaara, Royal Caribbean Cruises' executive vice president, maritime] comes back and says, 'Well, guys, if you want to have all this stuff, it's gonna be this big.'"

"All this stuff," as Bayley describes it, adds up to a variety of whiz-bang features. Perhaps the most prominent is the twin 10-story slides called "The Abyss," which earned their name from the muffled squeals of excitement you can hear from inside the tube as passengers twist and turn down the slide. Also aboard the Harmony, you'll find an ice-skating rink, two 43-foot rock-climbing walls, two surf simulators, a zip line, an outdoor boardwalk complete with a working carousel and "Central Park," an onboard green space filled with 10,000 plants and 50 trees. Even as you catch sight of the ship from afar, you'll likely be struck by its presence. At 1,187 feet long, the ship would be taller than the Eiffel Tower if you were to stand it on its rear.

Throughout the summer, Harmony will be taking passengers on seven-night western Mediterranean cruises out of Barcelona, Spain, and Rome (Civitavecchia), Italy, with stops in Naples, Palma de Mallorca, Spain, Florence and Naples. Fares start at $1,498.50.Harmony might take up the most space on the docks, but it's not the only boat making waves this year. Here's a look at the top ships to hit the high seas in 2016:

Ms Koningsdam

Holland America Line

Inaugural sail date: April

Holland America's newest ship, Koningsdam, is the first of the line's Pinnacle class. Koningsdam holds 2,650 guests and has a few new touches, including what the company says are its first purpose-built staterooms for families, plus staterooms for solo travelers. The increased size allows room for more public venues, too. In the ship's Music Walk area, passengers can enjoy different music genres, ranging from chamber music at the Lincoln Center Stage to blues at B.B. King's Blues Club. Koningsdam will be based in Amsterdam for a series of northern European and Baltic cruises this summer (its seven-day "Norse Legends" cruises start at $919). The ship will cruise the Mediterranean in September before heading to Fort Lauderdale, Florida, for its winter Caribbean season.

Royal Caribbean

Inaugural sail date: April

Royal Caribbean's 4,180-passenger Ovation of the Seas is the third of the cruise line's high-tech Quantum-class ships. Like its sister ships within the fleet, Ovation features frills like the gravity-defying North Star capsule, which takes guests 300 feet above sea level for 360-degree ocean views. The ship also has indoor bumper cars and RipCord by iFLY, an indoor skydiving simulator. Ovation's four-night July cruises from Tianjin, China, to Seoul (Incheon), South Korea, start at $1,138 per person.

Viking Sea

Viking Ocean Cruises

Inaugural sail date: April

Compared to other cruise ships launching this year, Viking Sea leans toward the smaller side: The ship can accommodate 930 passengers in its 465 cabins. Onboard, you can expect plenty of Scandinavian flourishes, including a two-deck Explorers' Lounge with decor inspired by Viking trade routes. Like its sister ship, Viking Star, Viking Sea also has an infinity pool. This summer, the Viking Sea will sail through Scandinavia, the Baltics and the Mediterranean. Its least-expensive itinerary – the 10-day, five-country "Empires of the Mediterranean" trip from Venice to Athens – starts at $2,999 per person.

Carnival Vista

Carnival Cruise Lines

Inaugural sail date: May

While Royal Caribbean may hold the title of world's biggest cruise ship, in terms of passenger market share, Carnival remains the biggest cruise line. The company's newest ship, Carnival Vista, carries fewer than 4,000 passengers, and roughly 1,500 fewer passengers than Royal Caribbean's Harmony. But Vista has plenty of bells and whistles, too, including a water park called WaterWorks, which has a 455-foot slide. The ship also boasts the SkyRide at SportsSquare, which allows you to pedal your way through midair. Cruise prices for eight-day summer Mediterranean sailings from Barcelona, Spain – with stops in Sicily, Rome, Florence and Pisa – start at $839 per person.

Regent Seven Seas Cruises

Inaugural sail date: July

With a 750-passenger capacity, the fourth ship in Regent Seven Seas Cruises is much smaller than the megaships setting sail today. Still, Regent is touting Explorer as "the most luxurious ship ever built." And it's making the case with its upscale main attraction: a 3,875-square-foot suite. The Regent Suite is appointed with two bedrooms and a large, private outdoor balcony. Most indulgent of all: an in-suite personal spa complete with a sauna, steam room and a spa treatment area offering unlimited treatments. The per-person brochure fare for this suite on the ship's 14-day maiden voyage from Monte Carlo is a jaw-dropping $143,998, but there's a 2-for-1 fare for $71,999 that includes airfare. The brochure fare for Explorer's lowest-level suite comes in at $29,998.

Seabourn Encore 

Seabourn Cruise Line

Inaugural sail date: December

Priding itself on offering a more intimate onboard experience than today's megaships, Seabourn's fourth Odyssey-class ship carries only 604 guests and some indulgent flourishes. Each suite will have its own private veranda. Plus, making its debut on Seabourn Encore is The Retreat, a rooftop sanctuary that includes 15 private cabanas, each with a flat-screen TV and a refrigerator filled with drinks of your choice (rates for the cabanas alone start at $350 per day). All this luxury, of course, comes at a price; fares for its December voyage – a 16-day Holy Land & Arabian Gems cruise from Greece to Dubai – start at $4,499 per person.

From: Travel.usnews.com