ONE MOMENT, I am surfing down the wave like a scene from Baywatch (well, almost). Then I lose my footing and feel I am suddenly in a Domestos commercial. It is as if someone has pulled an enormous chain and I am flushed, unceremoniously, through the system and into the overflow tank.

So, I grab my surfboard from the blue torrent and head back for more.

What makes it all the more surreal is that I am actually surfing 150ft above the German port of Hamburg, on a huge artificial wave.

But, then, nothing seems real when you are the very first passenger on board the largest passenger ship ever built.

Freedom Of The Seas is more than three times the size of the Titanic, four times the size of floating apartment blocks such as The World and longer than the Eiffel Tower. In fact, it is not so much a ship as a small nation with an engine.

Fully-occupied, it - I daren't call anything this big 'she' - will carry 6,000 passengers and crew through the tropics at 22 knots, or 25 miles per hour in landlubber language.

Fresh from a shipyard in Finland, it has cost its owners, Royal Caribbean, Pounds 510million.

Britain will get its first glimpse this morning when all 160,000 tons sail in to the Solent (advice to sailors: if you cannot see a big white funnel and a plastic mountain on top, then you are looking at the Isle of Wight).

Freedom will then spend four days in - or around - Southampton before it crosses the Atlantic to start cruising in the Caribbean.

But I have managed to intercept it en route from Finland during its first refuelling stop in Hamburg.

It is absolutely immaculate, of course, because it is brand-new and no one except crew and constructors has ever set foot aboard, until I walk up the gangway. And I have it all to myself for a few hours until it welcomes its very first party - 3,000 German travel agents who have been invited on board for a guided tour and a knees- up.

So, with a shameless disregard for the international convention on sunlounger reservations, I have claimed my deckchair before the Germans. In fact, I have claimed all 2,000 of them.

As I wander, alone, around these 15 decks - it's a seven-mile walk - I find one of the most impressive engineering feats I have ever seen. Freedom is not classically elegant but then it does not pretend to be. Aesthetes can quarrel about its design but the scale is simply awesome.

Running down the middle is a 400ft shopping mall six storeys high, which will accommodate a Disney-style circus parade every night.

THE 1,300-seat main theatre is larger than many West End venues. The theatre next door is nearly as big and also has an ice rink. And no other ship afloat can boast a water park, a boxing ring, a 43ft climbing wall, a 14-bed suite and a surfing machine which produces an all-day Bondi Beach wall of water. And it requires a full gale before this thing even feels the waves.

Such impudence is almost asking for a poke from Neptune's trident.

Until now, the biggest ship in the world - apart from an oil tanker has been the Queen Mary 2. But this beats Cunard's tub by 10,000 tons and 2,000 passengers.

'Freedom is a cruise ship and Queen Mary is a liner,' explains the Captain, Bill Wright, 52. 'Liners were designed for transportation; they're about speed and putting different passengers in different classes. Cruise ships are about fun.' It cannot be much fun sailing this thing, though. After Capt. Wright sailed out of Finland, he had to squeeze under Denmark's Great Belt Bridge with only 9ft to spare.

When he arrived in Hamburg and turned his 1,112ft baby round to point out to sea, he had 30ft to play with at each end. It is like driving a bus round the aisles of a supermarket. But as the company's senior skipper, he points out that Freedom has been installed with the latest in precision technology.

With three propellors at his disposal, he can actually turn this thing round on the point of a pin.

I have never been in a cruise ship before. I had assumed that they were all retirement barges full of bridge tournaments, blazered cads preying on unattached ladies of a certain age, furious social oneupmanship, celebrity lectures, clapped-out musicians and relentless eating.

But cruising is increasingly popular with all ages, and the British are second only to the Americans in their enthusiasm: more than a million Brits take a cruise each year - that is more than go skiing.

Little wonder that Freedom's American/Norwegian owners, who have 29 ships, employ nearly as many people as the Royal Navy.

On inspection, my preconceptions are largely unfounded. Freedom resembles a Florida holiday resort rather than Torquay, circa 1955. However, I am right about the food. This place is heaving with grub - ten restaurants, a threestorey dining room, 16 bars and 258 waiters.

I start at the top and work down.

Rising up behind the funnel is a 43ft climbing wall. The summit is 208ft above sea level - as high as the tips of Tower Bridge.

I may be the first climber to attempt an ascent but I am a disappointment.

I get about half way up when I start to lose my footing. This is not a problem as I am harnessed to a rope which is connected, via a pulley, to Carly Burnup, 24, a fitness instructor from Swindon. I let Carly take the strain and dangle to and fro above Hamburg, taking in the view.

At the stern, the surfing pool makes a deep rumbling noise as it pumps 34,000 gallons a minute up a broad plastic slope. It's a chilly morning and the water is not heated this ship is designed for warm weather - so I borrow a wetsuit. To guffaws from the contractors who are still painting the railings, I keep crashing and splashing and being flushed into the overflow tank until, finally, I get the hang of it.

Stretching out towards the bow is an archipelago of swimming pools forming a huge water park called the H20 Zone which is split into child and adult sections.

Downstairs, I am the first punter to warm up in one of the 20- seat, cantilevered whirlpool baths built out over the side of the ship, 100ft above the sea. You wouldn't get one of these in a liner. Next door is the largest gym afloat - an acre of machinery, spas and saunas, with a boxing ring in the middle. Resident boxing pro Rob Tynan, 26, from Dublin, puts me through my paces. I wouldn't like to meet him in a real fight.

AFTERWARDS, I change in my cabin - or 'stateroom' as everything is called round here. It's one of 842, with a balcony over the sea, a huge bed and a small bathroom.

Some of the larger suites come with grand pianos while all 1,817 cabins have plasma screens and non-stop films. Presumably, some slobs will never get out of bed.

One of umpteen glass elevators takes me down to the 'royal promenade', a shiny shopping 'street' full of brand-name stuff, several pubs and even a place where passengers can hire evening dress. There is absolutely nothing to suggest that I am in a ship. This could be a mall in Miami - or Manchester.

On the next deck, I find karaoke bars, casinos and the ship's TV studio - naturally, it has its own station - before stumbling across the theatre.

It is empty so I help myself to a pair of skates and stagger around the ice rink. But it is late afternoon and the German travel agents are starting to come aboard.

Before dinner, everyone gathers in the mall for the very first circus parade, a light-hearted affair complete with stilt walkers and inflatable elephants. The dining room, with 1,500 seats on three floors beneath huge chandeliers, feels like an opera house.

And right in the middle sits that cruising institution, the Captain's Table. Since it seats only 12, I ask Captain Wright how he picks a dozen guests from a possible 4,500. 'I usually pick some of our most loyal customers and some people who never imagined they would be asked at all,' he says. Tonight, though, he must hold court with 12 of Germany's leading tour operators.

I choose shrimps and a decent bit of beef from a sizeable menu. On a seven-day Caribbean cruise - they start at Pounds 1,463, including the flight from Britain - all the food is free while the booze is extra. Tonight, however, the booze is free, too. And these travel agents are on a roll.

They are cramming the bars, the dance floors and the theatre where a Best Of Broadway show is in full swing. I find a seat in the Schooner Bar where American entertainer Matt Yee is playing singalong piano in a wig and pretending to be Whitney Houston. Down in The Crypt, the soundproofed two-storey nightclub, the beat thumps on into the early hours. One well-refreshed travel agent is incapable of travelling one yard and has to be helped out in search of fresh air.

I have not been able to find anyone, anywhere playing a game of bridge all night.

And so, the largest cruise ship ever built begins its career of gentle hedonism and gargantuan consumption.

But Freedom had better enjoy its supremacy while it lasts. Royal Caribbean is already using the same Finnish shipyard to build the next generation of sea monster for a 2009 launch. Provisionally called Project Genesis, it will be 60,000 tons heavier and 100ft longer than Freedom, with a staggering 7,500 passengers and crew.

It, too, is supposed to end up in the Caribbean. But I can't help asking myself: will it fit?

SURFING POOL 34,000 gallons per minute swishes up the huge plastic slope to create constant waves CLIMBING WALL Its summit is 208 ft above sea level - as high as the tips of Tower Bridge GOLF COURSE 9-hole miniature golf course and simulators which recreate some of the world's finest courses DINING ROOM It seats 1,500 guests - but still only 12 per night are picked for the Captain's Table WHIRLPOOL Each whirlpool seats 20 people - dangling over the side of the ship, 100 ft above the sea ICE SKATING RINK 750 seats and a retractable floor cover for ballroom dancing NIGHTCLUB 'THE CRYPT' Completely soundproofed so no cabin is disturbed THEATRE Seats 1,300 people with Broadway shows and conferences CASINO 19 gaming tables and 308 slot machines TV STUDIO Produces daily programmes and recordings of the previous evening's entertainment BOXING RING It is the only permanent ring in the world on board a ship SHOPPING CENTRE 400 ft long and six storeys high, it hosts a circus parade nightly

FACTFILE

Length: 1,112ft Width: 184ft Height: 237ft Draft: 28ft Passenger Capacity: 4,375 Total crew: 1,397 Speed: 21.6 knots (24.86mph) Gross tonnage: 160,000 tonnes The ship is made of 3.7 million square feet of steel plate It is covered with 111,000 gallons of paint It contains 100 miles of piping and 2,200 miles of electric cable It generates 713,000 gallons of fresh water every day It makes 78,000 lbs of ice every day It weighs more than 80,000 cars or 32,000 adult elephants The water in the swimming pools weighs 530 tons The largest cabin is the Presidential Family Suite with four bedrooms, four baths and an alfresco whirlpool The length is equivalent to 37 double decker buses There are 750,000 lightbulbs on board