Then came a long shriek. Our eyes tracked upward from the cruise ship's Boardwalk area, past the eight decks of balconies overlooking the expansive, Coney Island-style walkway ... and there she was! A woman in a harness, her legs dangling precariously.

Her feet soon struck a platform, and she was pulled completely upright, smiling triumphantly after completing the ship's zip-line track, a first in the cruise industry.

Later on, as midnight beckoned, a couple descended the stairs toward the Royal Promenade, where the disco beat of "In the Navy" by the Village People was pounding. The pair was still dressed in formal dinner attire — tie loosened a bit — and the man remarked, "I'm having fun. I'm losing energy, though."

A seven-day sailing seems hardly enough time to savor all that Oasis of the Sea offers. It was launched in December as the largest, most ambitious cruise ship ever built, and Royal Caribbean International will add a twin ship, the Allure of the Seas, in December.

We boarded Oasis in January for the ship's seventh tour of the Eastern Caribbean, its standard itinerary, and it turned out to be the first full-capacity sailing: 5,638 guests and 2,218 staff and crew. How then, with nearly 8,000 people aboard, did my wife and I find ourselves alone for half an hour one evening, luxuriating in a sky-view hot tub that could easily accommodate 30 people?

It must have had something to do with such rotating choices as an almost-Broadway-caliber performance of the musical "Hairspray"; a rousing, Cirque de Soleil-style water show, "Oasis of Dreams"; an ice-skating extravaganza, "Frozen in Time"; a comedy club; jazz venue; casino; wine bar; and dozens of other restaurants and nightspots. A cruiser's energy will surely be sapped before the depths of Oasis's offerings are plumbed.

"Some cruise lines are known for their food; others, like Carnival, are known as party ships," said one veteran cruiser we met. "Royal Caribbean is known for its entertainment."

Even when the shows aren't on, though, the ship doesn't feel overcrowded. It's possible to slip away to a private spot, and we never had trouble finding a breakfast table, a deck chair, or a quick elevator. If you prefer certainty, it's possible to make online reservations for a meal or a show before you sail.

Six years ago, Royal Caribbean began planning its latest showstopping ship, in the tradition of Sovereign of the Seas (1988), Voyager of the Seas (1999), and Freedom of the Seas (2006), all of which debuted as the largest cruise ship at the time and introduced attractions such as rock-climbing walls, ice-skating rinks and surfing simulators. This odyssey began back in 1970 when the company launched the Song of Norway, which Bill Wright, the captain of the Oasis, called the first ship built specifically for cruise vacationing.

"Ocean liners had fallen out of fashion as soon as people could take a six-hour flight instead of a six-day crossing," said Wright, who spoke at a Captain's Corner event on our first day at sea.

Wright, who doubles as Royal Caribbean's senior vice president for marine operations and returned to that "day job" after our cruise, was involved in the planning of the Oasis from day one. He was joined along the way by Royal Caribbean's own designers and members of 37 other design firms, 20 architectural firms, and the STX Europe shipyard in Turku, Finland.

The "wow" features on the Oasis include the first outdoor park at sea, with more than 12,000 trees, plants, and flowers in the Central Park "neighborhood"; the carousel, the first ever on a cruise ship; the 80-foot zip line; the Rising Tide "floating" bar, which traverses three decks and leaves a multicolored waterfall in its wake; and an amphitheater across the ship's stern, with an 18-foot-deep pool and two giant LCD screens, that hosts the "Oasis of Dreams" show and movie screenings.

Indeed, when we docked at Nassau on the final day of our cruise, people on the Carnival ship next to us lined the railing to take photos and gawk at our "ride."

The 16-deck-high ship is as wide as an aircraft carrier, 208 feet, and that size equals stability. It also allowed for the unique design, in which the superstructure of the ship is split in half down its spine, with open space in the middle and several decks of balconied rooms on opposite sides looking out on either the park or the Boardwalk.

The seven distinct ship neighborhoods include the Boardwalk, Royal Promenade and Central Park, along with the pool and sports zone, the spa and fitness center, the youth zone (with daily children's and teen activities), and Entertainment Place, with its 1,300-seat theater, nightclubs, casino and ice arena.

We delighted in Central Park, with its winding walkways, four-story-high vines and ferns, and secluded benches and tables where people played cards, sipped wine, or dozed with a book or a crossword puzzle across their lap.

After two days at sea, our first port call was Charlotte Amalie on St. Thomas, in the U.S. Virgin Islands.

Instead of an expensive shore excursion, we purchased $12 wristbands that allowed us entry into five historic houses and a quirky amber museum. The self-guided tour gradually ascended the hills of this former Danish colonial port, capped by a view from the tower atop Blackbeard's Hill of the surroundings that make the harbor one of the world's loveliest.

The emphasis in ports of call (we also stopped at Philipsburg, St. Martin, and Nassau, Bahamas) is on jewelry and designer shopping. We skipped the hard sell and rented a couple of chairs and an umbrella to bask on a nearby beach for a few hours.

For many guests, cruising is about the food, and Oasis encourages people to never eat at the same restaurant twice. Oasis retains the traditional dining-at-sea experience in its three-story Opus dining room.

But with 24 venues on board, it's possible to hit them all if you add snack stops at places like the Boardwalk Donut Shop (free) or the Cupcake Cupboard (extra charge). The options top out at $35 additional for a meal at 150 Central Park, featuring award-winning chef Keriann Von Raesfeld, and $75 for a private "chef's table" dinner.

Oasis stats

Designers evaluated more than 15 configurations before settling on the final plans for Oasis, a 16-deck ship that's 1,184 feet long.

Oasis features the longest jogging track at sea on Deck 5: one lap is 0.43 of a mile.

The first beach pool at sea has a sloped entry so guests can wade in.

"Hairspray" is the first full Broadway show performed on any cruise ship.

Royal Caribbean commissioned some 7,000 works of art for the ship's public areas.

The Allure of the Seas, nearly identical to the Oasis, will launch in December.

The Boston Globe and The Seattle Times