Splashing out: the ocean liner that thinks big

She's longer than a queue of 40 Routemaster buses. She's taller than St Paul's Cathedral. She's as wide as a football pitch. Welcome to Royal Caribbean's brand new Allure of the Seas, the largest cruise ship in the world. On Tuesday evening she glided out to sea from her base at Port Everglades in Fort Lauderdale, Florida for a preview trip ahead of her official launch on 1 December.

But hold on. There may well be a sense of déjà vu here. It was only last December that Royal Caribbean's Oasis of the Seas was launched with much fanfare and amid similar superlative claims of being the biggest cruise vessel ever – a mega-ship with facilities to match. So how does that compare with this new mammoth property on the waves?

Created by the same shipbuilders in Turku, Finland, these sister ships both have a total capacity for 6,318 guests and are staffed by a crew of 2,384 while a great many features are also practically the same. However, the new, improved model Allure has the edge when it comes to the world record: she is 5cm longer than Oasis.

Stepping aboard Allure this week for a short three-night taster trip was a strangely bewildering experience. At Fort Lauderdale's huge new Port Everglades you can't actually take in the full extent of the vessel from the outside due to loading cranes and buildings. It is only as you board that you become aware of the spatial dynamics and you begin to appreciate the sheer scale of this enormous floating resort.

Your entry point is at the fifth of 17 decks, where you find yourself in a pedestrian street of cafes, bars and shops. And that sets the general tone. The entire ship, you gradually realise, is effectively a massive sea-borne mall – though one in which the emphasis is on food, drink and entertainment rather more than shopping. You're in a weird world-apart here, where reality starts fading fast. Should you begin to lose touch completely, it comes as something of a relief to see that the 24 lifts announce the day of the week on plaques in the floor.

Just outside those lifts, interactive maps guide you around the facilities. The options available on board are too overwhelming to enjoy at first: you need at least a day just to work out the range, quite apart from visiting them all. There's a park in a central eighth-floor atrium, open to the sky and complete with 12,000 plants and piped birdsong. There's a large "Boardwalk" area evoking Coney Island and featuring an old-fashioned carousel, an ice-cream parlour and a hot-dog outlet. There's a big spa alongside a well-equipped gym with jogging track below it. And of course there are pools. A total of 21 in fact, all dotted around Deck 15. Many of them are, admittedly, small whirlpools but there's a good-sized children's play pool, a sports pool and two "Flowriders", with simulated surf.

Despite all these attractions your attention soon becomes mainly focused on the ship's extraordinary range of entertainments. A programme of events is put in your room every day, from salsa classes and talks in the spa ("Look 10 Years Younger in 10 Minutes"; "Secrets to a Flatter Stomach") to family karaoke sessions, evening jazz and DJs. There's an entire entertainment deck with 3D cinema, comedy studios, a large Broadway-style theatre (featuring Chicago the Musical) and even, amazingly, an ice stage. And there's a "Youth Zone" catering separately for teens and younger guests.

But Royal Caribbean's biggest pride – and indeed joy – is its new association with DreamWorks Animation, makers of Madagascar, Shrek and Kung Fu Panda. Under exclusive licence, characters from these movies appear at intervals every day: dressed-up performers who feature in shows, street parades and "character" breakfasts. Disney might have had the idea first, but having hash browns with Shrek was a sure-fire winner with the six-year-olds, and indeed their parents, on our sample trip. Allure is pioneering DreamWorks at sea, but Royal Caribbean has plans to introduce these acts across many of its other 21 cruise ships.

The entertainments as well as activities and food (with the exception of a few specialist restaurants) all come as part of the package price. Meanwhile, you can almost forget the fact that you're at sea. Allure is so stately that you rarely feel any sensation of motion. When we set sail three hours after boarding, most of the passengers barely noticed that the ship had started purring out into the ocean.

We were sailing around in a small circle so our sense of a voyage was limited. But with such a large amount of entertainment and activity on board, the ship herself has become the focus of a holiday with the travel aspect just a minor part of the package. Perhaps that's just as well, since few ports can handle this behemoth – and her almost-identical twin.

Like Oasis, Allure will initially be operating two basic itineraries from Fort Lauderdale: the eastern Caribbean (calling at Nassau in the Bahamas, St Thomas, and St Maarten); and the western Caribbean, including the Mexican island of Cozumel and Costa Maya on the Yucatá* Peninsula. On the way she calls at Labadee in Haiti, where Royal Caribbean runs a private resort. It's a stark reality check to think of this state-of-the-art playground calling in on a nation of such need.

Ship-shaped: On the Allure

From the UK, cruises on Allure of the Seas are offered by a wide range of agents and operators, including Virgin Holidays Cruises (0871 781 9893; virginholidayscruises.co.uk) with eight-night holidays starting at £1,239. The price includes flights on Virgin Atlantic from Heathrow to Miami, transfer to Fort Lauderdale and a night (with breakfast) at the Westin Beach Resort followed by a week, full board, on Allure of the Seas.