It's very big, it's very orange and it's ultra cheap. The billionaire behind easyJet has launched a cut-price cruise liner. Simon Calder embarks for the maiden voyage

Imagine: you sail all the way from Bermuda to the Mediterranean aboard your $50m yacht, Golden Odyssey. You moor in the tranquil harbour at Nice, protected by the embrace of the Colline du Chateau. This mighty rocky outcrop, garnished with greenery, stands framed against a profoundly blue Provençal sky of the sort that seduced the Impressionists. Beneath it, an Italianate jostle of townhouses is soothed by pastel pinks and lemon yellows.

Imagine: you sail all the way from Bermuda to the Mediterranean aboard your $50m yacht, Golden Odyssey. You moor in the tranquil harbour at Nice, protected by the embrace of the Colline du Chateau. This mighty rocky outcrop, garnished with greenery, stands framed against a profoundly blue Provençal sky of the sort that seduced the Impressionists. Beneath it, an Italianate jostle of townhouses is soothed by pastel pinks and lemon yellows.

Next morning, you wake up to find that a bright orange blot on the seascape has berthed right next to you. Worse still, the quayside where you are tied up is crowded with journalists and their laptops. It puts waking up with Michael Howard in the shade. And speaking of shade: the sole member of the easyCruise fleet, easyCruiseOne, is obscuring the morning sun.

Stelios Haji-Ioannou is beaming as he strides around his floating pleasure palace. The Cypriot multi-millionaire, who founded the highly successful easyJet and numerous less flourishing brands, is on the brink of his next easyVenture. "This is bringing together my two separate skill sets," says Stelios. "It combines my experience in travel with my experience in ships."

His father, a shipping billionnaire, helped Stelios set up his own line, Stelmar. Haji-Ioannou Senior also provided financial backing a decade ago, when Stelios started the easyJet experiment that revolutionised aviation in Europe. The ebullient 38-year-old is hoping that easyCruise will subvert the traditions of cruising in the same way. "I'm trying to get younger people to start cruising."

In an ageing society, where the traveller with the time and the money to see the world at cruising speed is old, Stelios is rebelling against conventional wisdom. His orange odyssey is to entice a new generation of travellers on board, and to offer an independent-spirited cruise at prices way below the norm.

"My break-even is about 70 euros [£50] - that's roughly what I need per passenger per night." That translates to £350 a week, a bargain by Mediterranean standards - though unlike the usual cruise deal, your ticket for easyCruiseOne does not include meals or entertainment. But that is all part of Stelios's cunning plan: "This is not an ocean liner on which you're going to spend days and days at sea. Unlike traditional cruise ships, it sails at six in the morning, not six in the evening. If you were checking into a normal cruise ship today, at six o'clock when the town is about to come to life and the light softens, the ship sails and you disappear into the pitch black. You're captive on board the ship. It's much better to stay here and explore the town. You come back, fall asleep and the captain will sail the ship to the next port."

Sleeping is probably the best plan while on board, given the limited facilities. Leave the dinner jacket or cocktail dress at home, and don't expect an invitation to the captain's table. There is a gym, a sports bar and an outdoor cocktail bar - complete with jacuzzi. But with only 86 cabins, this is not a party boat: the party takes place on shore. And if, when you sail, you happen to have left something behind in a Niçoise restaurant, you could go back to retrieve it by cab within 20 minutes - the first destination for easyCruiseOne is Cannes, just 20 miles along the coast.

Many people cruise to see the world. Above the counter in the Caffe Ritazza, which serves as the vessel's main social centre, is a list of aspirational harbour cities - Sydney, Stockholm, Hong Kong, New York ... Initially, though, easyCruise offers a voyage for people who don't much like being at sea. In the course of a week, easyCruiseOne will stray no further than Genoa and Portofino, 120 miles away on the Italian Riviera. "It's about experiencing the Riviera from a vantage point that only owners of private yachts could do before, in the company of 169 of your best friends," says Stelios.

Parts of the travel industry, being just as bitchy as the fashion business and the media, make a predictable response to the expansion of the easyEmpire into cruising: a glorified ferry, they call it. Stelios refutes this. "A ferry takes you from A to B, and once you get there they kick you out to get the next bunch on board. They don't act as a hotel, they don't welcome you back at 4am after you've been out to the clubs - and they don't call into St-Tropez and Portofino."

If you really want to cruise aboard a glorified ferry, sign up for Hebridean Princess. She began life four decades ago as the Caledonian MacBrayne ferry Columba, shuttling between Oban and the island of Mull. For the past 16 years she has been cruising in the Western Isles, with a passenger manifest of some extremely rich people; some Hebridean Princess voyages cost over £1,000 a day. That sort of cash could buy you a month aboard easyCruiseOne, though you could develop a little cabin fever.

Stelios bought secondhand: easyCruiseOne began life as Renaissance 2, plying the Caribbean. She later became Neptune II, a gambling ship based in Singapore - which was where Stelios acquired and refitted the vessel. "You could call her a floating hotel", he suggests. Bluntly, though, she feels more like a floating youth hostel. The standard cabin has a couple of comfortable mattresses and duvets. No mini-bar, no telephone - and no window, unless you upgrade to one of the four suites. The relentless headache-orange decor could get to you after a while, too. But these are not rooms in which you are expected to do much more than sleep and shower - the latter in a clever, space-saving one-piece bathroom.

Contrary to earlier rumours, you need not clean up after yourself. "That was an idea I toyed with, and decided against it," says Stelios. "There's nothing wrong with making a course correction in a business." The deal is that if you want your bed linen and towels changed, you tell reception and pay £10. "Think of it as tipping the housekeeper."

Access to your room is achieved with a personalised room key: when you check in, you have to pose for a photograph that is imprinted on the key (mine bore a strange resemblance to a "Wanted" poster). This is the first human interaction that most customers will have with the easyCruiseone crew. As with the other easyEnterprises, you are expected to buy online (at The price for each night depends on how far in advance you book and how heavy demand is for the vessel. In two weeks' time, when the vessel is moored in Monaco for the Grand Prix, rates are very high; but conversely, you can pick up a week at the end of the season for below cost.

This weekend, the vessel has a 100 per cent turn-out. Stelios pronounces himself "very encouraged" with forward bookings, at least until October. No fewer than three camera crews from Sky One are on board, making a documentary series that could do for cruising what ITV's Airline does for no-frills flying. One spin-off for that programme is to give easyJet sales a boost every time it is screened.

Stelios will be watching the numbers, not the televisioni. He has yet to decide what to do with the ship in the coming winter, but as soon as the first passengers are on board he introduces himself and conducts some market research.

Neil Cobb and Janet Armstrong from Sheffield turn out to be almost ideal customers - except for the reason they are on board, which is to celebrate Mr Cobb's 50th birthday, thus puncturing the age profile.

"Our first thought when we saw it advertised was: 'Why hasn't anyone thought of this before?' I like the concept of waking up in a different place every day. But nine times out of 10 on a normal cruise you miss out on the nightlife," says Janet Armstrong.

Stelios buys them a beer and asks a hypothetical question: "Would you fly to the Caribbean to join this vessel?" He has not yet decided where easyCruise one will sail in the winter, but is evaluating an itinerary involving Antigua, Barbuda, St Bart's and St Martin.

Neil Cobb urges Stelios to design an itinerary to coincide with the England cricket tour of the West Indies, while in return the entrepreneur asks if they would be inclined to book a two-week cruise even if it meant duplicating the same group of islands. "Certainly," says Janet Armstrong. "Sometimes you don't get enough time in one place."

The crew will see plenty of the French and Italian Rivieras during the coming four months. As with conventional cruise ships, they comprise a cosmopolitan mix: predominantly Filipino and Indian, with a range of European nationalities - and a few strays from the Caribbean, who could be back home this winter if Stelios decides to despatch easyCruiseone across the Atlantic. Should the big orange tie up in an opulent destination like St Bart's, she may irritate more than just the millionaire yacht-owners.

At present, the cruise industry regards easyCruise as an amusing novelty. Peter Williams, sales director of Hebridean Island Cruises, sees easyCruise as the "polar opposite" of what his company provides. "We certainly don't see it as a threat, but we applaud all efforts to broaden the cruise industry."

Stelios is not quite so kind to the industry in return: "So long as they insist on cloistering their passengers on board every night, milking them in the casino, forcing them to play quoits and shuffleboard to while away the hours, they will never attract a young crowd."

The floating fun palace Stelios has created is reaching his target market: the average customer is aged 35. But once the inaugural weekend is over, cabins will start to empty.

"I haven't bet the farm on it," Stelios says. His total investment is a relatively modest $20m (£11m), less than the cost of an easyJet Airbus. More mega-yacht owners in the Mediterranean and the Caribbean could soon find themselves put in the shade by a big orange blot on the seascape.