This is it. The lumbering, slavering, glowering apex predator of the cruising industry, weighing in at 250,000 tons and 1,198 feet long – Royal Caribbean’s Icon of the Seas, biggest cruise ship in history.

It’s been many years in the making – and now at last it’s truly at sea. And so, to be honest, am I.

The experience, when I board in Miami for the inaugural sailing, is overwhelming. Ahead of me is an art work resembling a giant golf ball and a swarm of Royal Caribbean employees, all in orange T-shirts, standing attendance. Nearby, a man clutches a clipboard next to a life-size bronze sculpture of, for some reason, a dog relieving itself on a lamppost.

My short voyage coincides with the launch of a partnership between Royal Caribbean and the Inter Miami soccer team, whose squad includes one Lionel Messi. It’s an irresistible pairing. The greatest footballer of all time adopted by the greatest cruise ship of all time. Somewhat predictably, Royal Caribbean has taken to calling Messi ‘the Icon of the Icon’.

Thomas W. Hodgkinson enjoys a drink with his book as he lounges by the pool onboard.

Weighing in at nearly 300,000 tons and 1,198 feet long – Royal Caribbean’s Icon of the Seas is the biggest cruise ship in history.

With the size, and the hyperbole, and the sheer weirdness, it takes 24 hours to acclimatise. At first I hardly know which way I’m facing. And when I do get my bearings, I don’t turn a hair at the sight of an enormous plastic flamingo, nor when, on entering the all-you-can-eat buffet, I’m assailed by two exuberant Mexicans sporting surplices that resemble a doughnut and a fried egg.

‘How did you sleeep?’ asks the Doughnut in a sing-song falsetto. Not bad, I say. ‘Don’t forget to waash your haands!’ chimes in the Fried Egg.

This colourful wackiness is a world unto itself. Barely affected by the waves, it moves according to its own rhythms and rules.

Rule 1. You can have whatever you want. A breakfast cocktail? Help yourself. Basketball? No problem. A climbing wall? A shopping mall? We have you covered, sir.

Rule 2. Join in. There are so many activities on hand, it would be a crime not to try them. It’s a chance to do things you love, and a few you’ve never done before.

I explore the water slides, which sprawl over the top deck like haemorrhaged organs. The Pressure Drop is no big deal, as it turns out. But the Frightening Bolt is full-on.

One morning, I try the fastest-growing game in America. Pickleball is played on a small court, with a small plastic bat and a plastic ball. It’s easy to pick up and terrific fun.

Thomas practises his short game on a crazy golf course on the sunny deck aboard the huge ship

The Icon of the Seas boasts the world’s largest floating water park and infinity pool

The Ultimate Family Townhouse spreads over three floors, sleeps eight, has a musical staircase and a slide. It can be yours for £70,000 a week

That afternoon, I join a napkin folding class. Because I figure: if not now, when? In the event, there has been a mix-up and there’s no teacher. Luckily, another punter – Mike from Dallas – works in the catering industry and steps in to take the class. Soon I am absurdly proud of my Diamond Fold. Returning to my room, I fold all the linen and towels into diamond shapes.

My ‘stateroom’ is nice, incidentally. Not huge, but smartly put together, with a balcony and sea view. All for around £2,600 a week.

For the bigger spenders, there’s the Ultimate Family Townhouse. Spread over three floors, and sleeping eight, it has a musical staircase, and a slide. It can be yours for £70,000 a week.

Having built the world’s largest passenger ship, with the world’s largest suspended infinity pool at sea, and the world’s largest floating water park (and so on), it’s unconvincing when Royal Caribbean claims to have no obsession with size. ‘The size thing happened by accident,’ insists Jay Schneider, the company’s chief product innovation officer. ‘We never set out to make the world’s biggest ship. We just wanted it to be the most iconic.’

You can have whatever you want. A breakfast cocktail? Help yourself. Basketball? No problem. A climbing wall? A shopping mall? We have you covered, sir

A bar onboard the liner. Jay Schneider, Royal Caribbean’s chief product innovation officer said: ‘We never set out to make the world’s biggest ship. We just wanted it to be the most iconic.’

A state room on the luxury liner, with a sea view, costs £2,600 a week

Every few years, though, the company happens to make a ship a few feet longer than the last one. It’s oops, we did it again.

More convincing is the company’s claim to have created the world’s greatest holiday for children. Forget Disneyland Paris. This theme park floats. For little ones it’s going to be sheer heaven.

They might even find themselves playing pickleball against some of the world’s greatest footballers. At the end of my trip, for the naming ceremony, the whole Inter Miami squad – including Luis Suarez and Messi himself, turns up on the ship in their pink strips. As a reward, they are given vouchers granting them and family members a cruise any time they like.

Which must be some comfort to Messi – who is estimated to have earned $1.15 billion (£900 million) in his career so far, according to Forbes.

There follows a suitably mad extravaganza in the spectacular Aqua Dome. There’s a bagpipe performance from a rock band called the Red Hot Chilli Pipers; blessings from a rabbi and a priest. Then the great Lionel Messi dutifully smashes a vat of Veuve Clicquot against the hull, declaring: ‘I name this ship Icon of the Seas.’

And it’s job done – until the next biggest cruise ship in the world comes along.