Carry on cruising

So, let's get this straight. Two thousand guests board the ship and meet one of the three greeters. If each guest makes an average of four Titanic jokes apiece, and there are 40 cruises each year, that makes a horrifying 320,000 annual Titanic jokes on this boat alone. The effect of that one movie on a global industry - and the economies of the Third World countries that cruise ships touch - cannot be underestimated. The number of these floating behemoths has risen from 85 in 1996 to 210 today. Summit, the ship I am joining, carries the largest spa afloat and makes her ponderous, stable way around the world from the Caribbean to the Norwegian fjords. I'm travelling on a four-day cruise from Fort Lauderdale in Florida, stopping at Key West and Cozumel, a Mexican Caribbean island. Built in 2001, the Art Nouveau dining rooms and fin de siècle touches only serve to remind you that you're here partly because people just loved watching all them folks drown.

So, let's get this straight. Two thousand guests board the ship and meet one of the three greeters. If each guest makes an average of four Titanic jokes apiece, and there are 40 cruises each year, that makes a horrifying 320,000 annual Titanic jokes on this boat alone. The effect of that one movie on a global industry - and the economies of the Third World countries that cruise ships touch - cannot be underestimated. The number of these floating behemoths has risen from 85 in 1996 to 210 today. Summit, the ship I am joining, carries the largest spa afloat and makes her ponderous, stable way around the world from the Caribbean to the Norwegian fjords. I'm travelling on a four-day cruise from Fort Lauderdale in Florida, stopping at Key West and Cozumel, a Mexican Caribbean island. Built in 2001, the Art Nouveau dining rooms and fin de siècle touches only serve to remind you that you're here partly because people just loved watching all them folks drown.

The cruising demographic has also changed over the past few years. The explosion in the number of packages mean that there are fewer old ladies with morning jewellery and ice-whip hair playing parcheesi than expected, although fortunately some remain. Drinks and party games round the pool ensure that there are lots of couples and groups of friends like any package tour, while all the single people on board are reading The Da Vinci Code. And with them have come lots of new things to do: massages; thalassotherapy; golf simulations; basketball courts; bingo; a casino.

Of course the more traditional aspects remain: quoits, deck chairs and, naturally, the food. It is extraordinary that these enormous moving structures are prized chiefly for their ability to dole out limitless supplies of munchies at 2am. There are 14 meals a day, plus free 24-hour room service and constant snacks on offer, and there are lots of different places to eat, so nobody notices if you go from one to the other and eat four times. You realise that humans are, fundamentally, no different from your dog - remember the time that you forgot to lock the kibble mix away and he tried to eat himself to death?

There are 48 items on the breakfast room service menu alone, all of which are included in the price. As I am going to bed one night at midnight, the lift pings, and a gigantic man walks out, sombrely clutching an enormous melting bowl of ice cream. I choose to believe that he is on his way to spread it all over his wife.

Key West, our first port of call, is a pretty town - the southernmost in the US and the home of Ernest Hemingway and Tennessee Williams. It's now very geared to the tourist trade, which makes it easy to jump off for a couple of hours and take the museum tours, which are fascinating, if a bit rushed. It's difficult to concentrate on the gingerbread houses when part of you is thinking, "the boat's going to leave without me! It is, it is!", but the locals are experts on cruise schedules and won't leave you high and dry. Back on board, America falls behind as the boat takes off, surprisingly smartly, and it's time to settle into ship life.

To have the complete cruise experience you must go to "the shows". The cinema is screening Master and Commander (presumably so you can have a good chuckle at the lack of spa facilities available to Russell Crowe in the early 19th century), and Finding Nemo, perhaps so you'll know what to do if you fall overboard. The shows, while featuring girls who can dance in high heels (a talent I have always secretly admired), are as camp as you'd expect, with lashings of Lloyd Webber, robot costumes and the heartfelt emoting that comes from performers reliving the pain of failed auditions. My particular favourite is Encore, in which singers perform tributes to various stars. One man, sitting at a piano, rises up on to the stage to play "Piano Man", while video screens overhead show footage of Billy Joel, perhaps in an attempt to convince the older passengers that they're watching the real thing.

There's also a singles meet at midnight every night in the Revelations disco, where you can trot along and members of the crew in their smart white uniforms will ask you to dance. Somewhat poignantly, a note in your brochure says: "If there is a member of staff you would particularly like your photograph taken with, do let us know and we will arrange an appointment." There is a karaoke tournament too, performed by Americans to such a high and competitive standard it's hard to tell it's karaoke at all. On the last cruise a woman won with a rendition of, yes, Celine Dion's "My Heart Will Go On", having announced: "I'd like to say how honoured I am to sing this song". Thankfully, after an hour of flawless performances, two British guys get up, take off their tops and screech "Genie in a Bottle" while fondling their man breasts, thus keeping our national pride intact.

One very important thing to remember if cruising is for you is that timing is paramount. Everything happens on the dot, and there is a lot of queuing to get on and off things. If you want to do things on the ship like have a spa treatment, use the golfing simulator or eat in the à la carte restaurant, you have to book well in advance.

The organisation of cruises appeals to those who like structure in their lives, so it's no surprise that there's a lengthy policy document on behaviour that's written out in that folksy US style of charm and threat patented by George W. For using offensive language or wearing the wrong clothes to dinner you will be warned twice then politely removed by security. If, however, you are caught with a shipment of heroin, it will merely be confiscated in line with the laws governing international waters.

A word of warning: while more British ships are starting to offer an optional service charge, on the American ships (as this is), the constant sit-up-and-beg gratuity system still exists, with little envelopes delivered to your room and people asking whether you are missing your family. The average member of staff is from the Philippines or Mexico, and works eight months on, two months off, eight months on, in fairly full-on conditions.

After a day we arrive in Cozumel, which has a long list of things you might like to do. The excursions are, exactly like those on package holidays, expensive and optional, although they come with the added frisson that if you don't get back to the ship in time it'll sail without you. Pat imprisoned dolphins on the head, get on to a slightly smaller "party" boat to drink stuff from hollowed-out coconuts and flash at other boats, dash around museums or simply stroll and marvel at what the cruising industry does to entire communities. One of our party had been here 16 years before, "and there was nothing here at all", she says, taking in the shoddy construction, turquoise-and-cheap-silver warehouses, hucksters with fringed clothes, meterless taxis, $6 cans of coke, water parks and T-shirts bearing the slogan: "Lost the hair but the dick's still big...COZUMEL".

"Remember, we care about the environment," says the captain of this 91,000 ton vessel dedicated to pleasure. (A cruise ship releases air emissions equivalent to 12,000 cars and produces about 20 tons of solid waste a day). "Foxy the dolphin, she ees saying 'keep my ocean clean'", says the trainer at Cozumel, where the clicking Foxy is kept in a cage 10 metres square. At the moment they're training her to keep away from her baby so they can train the baby up too.

On a boat carrying 3,000 people (2,000 guests, mostly American, and 1,000 staff) it's surprisingly easy to hide if you stay away from the pool, where there are games of the orange/crotch-interface type going on, making it a little like a redneck Butlins. The libraries are deserted, and the back of the ship is quiet - perfect for drinking a glass of champagne in the setting sun without anyone trying to force you to have a snack or take a melon-carving class.

If cruising is the kind of thing you've always wanted to do, the Summit is certainly a lovely example. After widespread problems with food poisoning on some ships last year it is spotlessly clean, and there's some rather witty art dotted around including a lovely brass reimagining of Duane Hanson's The Tourists on the uppermost deck. And while the old truism of being very wary of any fun that doesn't let you get off when you've had enough still holds, the sea is restful, your mobile won't work, there is Scrabble to be played and champagne (you get a free bottle in concièrge class) to be drunk.

You wake up somewhere new every day, and every conceivable decision has been taken out of your hands, making it easy to enjoy yourself in peace, safety and comfort. Much, though, remains surreal. On the last day, you can wander through the picture gallery to see all the official photographs taken of the guests. There are shots of a lot of people standing in front of a staircase I don't recognise. "Where's that?" We peer at it. Yes, it is a painted backdrop of the staircase from Titanic. Guests have chosen to stand in front of this to have their photograph taken as an official memorial of their holiday. The mind boggles. And after watching 60 waiters perform a dance while carrying lit baked alaskas on the final night, we are asked to join in a chorus of "Auld Lang Syne".

"Why?" I ask. "This wasn't in Titanic, was it?"

"No," says my friend. " The Poseidon Adventure, you idiot."

TRAVELLER'S GUIDE

Jenny Colgan travelled with Celebrity Cruises (0800 018 2525; www.celebritycruises.co.uk) on the Summit on a four-night cruise from Fort Lauderdale. Prices for this occasional cruise cost from £749 for an outside cabin, cruise only. Summit is sailing a series of 12-night Ultimate Caribbean fly/cruise holidays from Miami or Fort Lauderdale from mid-October to December 2004. Ports of call include St Maarten, St. Lucia and Barbados. Prices start from £1,249 per person, including flights, all accommodation and entertainment on board ship.

From July to December, the Celebrity cruise ship Century offers nine-night fly/cruises from Miami or Fort Lauderdale. Prices start at £919 per person, including flights, all accommodation and entertainment on board ship.