The world's largest cruise ship will be launched from Southampton this weekend. Built at STX France, St Nazaire, France, Harmony of the Seas, is Royal Caribbean International's 25th ship and will take over from the Allure of the Seas as the largest in the world, albeit by just a couple of feet.

And while, for most the focus is on the ship's potential for a holiday, behind the scenes lies a very intricate business. Irishman Derek McKnight, who hails from Co Cork, has a pivotal role in this global organisation. Currently food and beverage director on the Oasis of the Seas, one of the three Oasis class ships in the Royal Caribbean fleet, he has been the start-up executive chef on both of the company's previous giant cruise ships and will be taking over as food and beverage director on Harmony in the new year.

To get some idea of the scale of Harmony of the Seas it is the length of 32.5 double decker buses laid end-to-end, or four football stadiums. It weighs in at over a quarter of a million tonnes, making it heavier than every single car sold in Ireland last year combined.

The ship is 18 decks high and, if stood above the waterline, it would tower over Dublin’s Liberty Hall by 40ft.

The four bow thrusters carry 7,500hp each and the number of guests at full capacity total 6,410. This doesn’t include the 2,300 crew and staff bringing it up to a whooping 8,500 people on board at any one time.

Approximately 46 different nationalities are represented in the food and beverage team onboard giving the Corkman a whole world of employees to work with.

When I first met Derek he was based on Allure of the Seas and showed me around the workings of his finely tuned kitchen.

I asked him what was the biggest contributing factor to his success with such a massive global corporation. "Communication" was his quick reply. Communication was the key to a smooth operation. Three years on, and since appointed food and beverage director of Oasis of the Seas, he holds the same values but on a much larger scale.

"When I take over as food and beverage director on board Harmony next year, I will have overall responsibility for the 100,000 plated meals produced per day."

Full all year around, Harmony of the Seas will be based in Europe for its inaugural season.

Impressive résumé

After graduating from Rockwell Hotel School in Co Tipperary in 1989, Derek has built an impressive résumé.

“I was a bit of a black sheep in school,” Derek says, a trait that may ring familiar with many of the country’s most successful business people and entrepreneurs.

The call of the sea tempted him immediately after graduation and he started his working life on the QE2, sailing out of Tokyo. Derek worked on Cunard's flagship from 1989 until 1996, when he went to the Cayman Islands, joining the island's first five-star hotel, as executive chef.

In 2003, he moved back to Ireland and opened his own bar and restaurant in west Cork, and became executive chef of the four-star Maritime Hotel in Bantry. But, five years later, he returned to the ocean with Royal Caribbean International. Back in 2008 the Freedom of the Seas was the biggest cruise ship and he was appointed executive chef.

And how much had things changed at sea in that time.

“Keeping in touch with home is easier these days,” Derek says. “With Skype and Facebook, I keep in touch with home every day and, if I have to work over Christmas, the entire family can join me in the Caribbean on the ship.”

He works four months on and two months off, because there is no time-off on board the ship. The buck stops with him regarding all major food and beverage decisions on board.

“As soon as I walk up that gangway, it’s power, power, power, for four months,” he says. “I’m always on call because it’s a 24-hour operation.”

So what can guests expect in the restaurants on the new ship. Derek runs through the details of the range of speciality restaurants on Harmony, including Izumi, Hibachi & Sushi, with a new teppanyaki menu, and the Sabor Modern Mexican restaurant. The new Wonderland Imaginative Cuisine will give guests the chance to experience a unique culinary adventure for the senses when Royal Caribbean chefs twist their culinary kaleidoscopes with never-before-seen fare.

In total, with 31 bars, restaurants and cafes, Harmony will be offering the largest range of food and drink available at sea.

The figures are daunting. The new ship will need 50 tonnes of ice cubes and almost two million litres of fresh water every day. On an average seven-night cruise, an Oasis-class ship requires, 5,000 dozen fresh whole eggs, 100 gallons of chocolate ice cream, 2,100lbs of lobster tail and 2,500lbs of fresh salmon onboard.

When Derek returns to Schull, he enjoys the good life and likes nothing better than working in his garden.

“When I’m on leave, I enjoy walking on beautiful Barleycove Strand,” he says. “On a typical day, my wife is at the gym, the kids are at school and I like nothing better than to go out to the garden and work in the vegetable patch.

“My family love to see me come home with a suitcase full of presents, and they love to see you me go too after my two-months off.”

Royal Caribbean introduces a new spectacle with each ship and Harmony of the Seas is no different. It will boast the tallest slide at sea, Ultimate Abyss is 100ft tall, and starts 150ft above sea level with guests making the descent, off a see-through platform into 216ft of tunnels, at an average speed of 9mph. Jumping from the top of Ultimate Abyss is just short of jumping from the top of Rio de Janeiro's Christ the Redeemer statue.

For his part Derek will be in the bowels of the ship, managing the catering fare. Although he is mostly based in the Caribbean, Royal Caribbean Cruise line’s 25 ships sail destinations in the Caribbean, Europe, Alaska, South America, the Far East, and Australia.