'Could you fit mine with a shark aquarium?' 'Certainly, sir'

Economies are sinking, but the super-yacht industry is surprisingly buoyant. Tom Peck dips into a world where anything is possible

From the private hot tub high up on the owners' deck, all that can be seen is the sun shimmering on the azure waters of the Adriatic. This is less "how the other half live" and more how the other 0.00002 per cent live.

Ancona, a pretty but not vastly wealthy town in northern Italy, is home to one of the world's few builders of mega-yachts for the mega-rich, CRN Spa. While the company's clientele occupy a niche – it estimates that there are just 1,500 people in the world wealthy enough to consider buying a boat from them – business, even in an era defined by economic hard times, is steadily improving.

Those 1,500 people are not who you might expect. "[Basketball star] Shaquille O'Neal, he's rich," goes a famous joke by the American comedian Chris Rock. "The white man who writes his cheque, he's wealthy." It is a sentiment echoed here. "I know the names of all our clients," says the boatyard's chairman, Lamberto Tacoli. "They're not famous people. You won't have heard of them." The mega-yachting world is the preserve not of Premier League footballers or Hollywood stars but of international businessmen (and it is men – the company is yet to secure its first female buyer).

Their names may not trip off the tongue but, chances are, in one way or another, money that was once in your bank account is now in theirs'.

"We are talking billionaires," says sales manager Matteo Belardinelli. "They are the kind of gentlemen not used to hearing the word No."

I have not arrived at the Ancona boatyard with the requisite €85m (£73.6m) for one of their 80-metre yachts – the largest they have built – but I have brought along some ideas for a vessel of my own.

Aquarium with sharks, please?

"Aquariums are not uncommon, we have built many boats with large aquariums. Sharks? If it is big enough, why not?" agrees Mr Belardinelli.

Submarine?

"We have never been asked for a submarine. There are one or two yachts out there with submarines. It would be a challenge, but we could do it."

Lion enclosure?

"Hmm. We can provide almost anything but on some things, we have to be fairly tough. Clients often don't realise they won't want the things they think they do. You want them to enjoy the boat and have the maximum quality of life."

Such outlandish requests are as nothing compared to those a luxury yachtmaker must routinely satisfy. A few years ago an American client arrived and had signed a contract to buy a 43-metre yacht within two hours, with a price tag of €25m (£21.6m). He had never owned a boat before. "He told us: 'The interiors, the colours, the finishes, I don't care. The only thing I care about is the safety of my dog, as the boat is a present for her.'

"On boats you have big holes, big gaps, big open spaces where a dog might fall – and this was a very small dog," Mr Belardinelli explains. In the end he spent over a million euros having the holes closed over with glass and netting.

"When it was nearly finished I called him just to ask what colour he wanted the exterior of the yacht to be. He said: 'I don't care,' and he hung up on me. I called him back and he did it again. We went for light grey in the end. When I drove it in to Monte Carlo where he was waiting to take delivery of it, I was a bit nervous to say the least. But he was happy with it, and he named it Katie – after his dog."

In the yard at the moment is a half-built 58-metre yacht. Its buyer has requested it be painted to look like a military vessel. At the rear will be a "floating garage" containing several speed boats. When the door opens, water rushes in filling the garage, allowing the owner to drive out, presumably in a tuxedo and carrying an unstirred but well-shaken martini. When they return, nuclear crisis averted and casual copulation secured, they drive the boat back in and seal the door. Then special pumps empty the garage again.

Another of their yachts houses a 7.5-metre sailing boat on the upper deck, which can be lowered in and out of the water 20 metres below using a specially designed crane.

The billionaire clients are of course rather busy people, so when it comes to fixtures and fittings, a prestige yachtmaker finds that it is often the wife or girlfriend they work with more closely, which can present certain challenges of its own.

One lady, the wife of an "Eastern European gentlemen", apparently, spent €3.5m on Swarovski crystals, which were attached to, well, everything. In the finished vessel, the great chandelier in the main dining room matched the flip-flops worn by guests.

She also requested a real wood fire, right next to a silk and cashmere carpet that cost €750 per square metre. "That was quite a challenge."

Mr Tacoli cautions the fashion-conscious sailor: "It will take probably three years from ordering a boat until final delivery. In three years, fashions change, tastes change, and often the wife or girlfriend changes too. You have to manage that change."

One buyer's mistress instructed them to fit out all the interiors with black marble. Then his wife arrived and made them change it all.

Of course, for every rule there is an exception. "One client, he told us, 'Listen. You do not let my wife in here. This boat is mine. Not hers. I will decide everything.'"

For such owners, their boat is a second home, a temple on the sea, tailored to their dreams. Others have half an eye on resale value, or on its potential as a private charter. One of CRN's yachts, Maraya, has been chartered several times by P Diddy (with an estimated wealth of only $475m, or £288m, he doesn't quite make the 1,500), at a cost of €400,000 a week. On one such occasion, a nameless but "very high-profile, English model" attended a party on Maraya at which she was told to stop jumping up and down on the rather expensive flooring. "Don't you know who I am?" she apparently screamed. "I do. Do you know who I am?" came the reply. "I am the captain. Stop jumping up and down."

Often the owners, canny businessmen that they are, arrive at the yard unannounced to check on the progress of their new toy. "One guy, an American," explains Mr Belardinelli, "he called the office and said, 'Can you see me?' I said no. He said, 'Look out the window.' He was flying his helicopter in the yard, leaning out the window, laughing and giving us the finger."

Currently under construction, and two years away from delivery, is an 80-metre behemoth, the biggest they have ever made. The client is an unnamed "middle eastern man". A King? "Not yet," comes the answer. Next week the same family will take delivery of a brand new 60-metre vessel. This 80-metre one will be their fourth.

The interior currently resembles a building site, and pictures are not allowed, "for safety reasons". The finished vessel will have room for eight body guards to stay. The top storey is the private owners' deck, where currently sits the shell of what will be a full time and, fully staffed, hairdressers' salon, for the exclusive use of the owner's wife.

This boat, as with others, will come with a specially developed iPhone app, showing the owner the precise location of all of his 30 crew members. Should he require attending to, he can then call the one nearest to him. Another app allows the owner to control the onboard CCTV cameras and see what everyone is up to.

The residents of Ancona, a small port town which, coincidentally, happens to build playthings for the super-rich, seem proud of their industry. When, two or three times a year, a yacht is launched down a ramp, children clamber up walls to try and glimpse inside. When the Middle Eastern gentleman's boat is finally launched, 12 special trolleys will have to be hired to carry it from the shed on to the ramp, at a cost of some €800,000 for a single day. They are driven electronically by a chap with a remote control who, Mr Belardinelli says likes to have a cigarette hanging from a corner of his mouth as he does so. "It is terrifying to watch," he says. "Absolutely terrifying."

Whoever the middle eastern gentleman is, he is evidently among the more traditional clients. But the market is changing, and the future is unpredictable. The credit crunch wiped out many shipyards, which in the boom years had started to build boats before they had found a buyer for them, in the belief that the shorter waiting time would lure in customers. Then the rudder rather fell off the bottom of the financial world, and the customers sank without trace.

CRN chose not to speculate on buyers, a decision that proved profoundly wise. Now things are rather better. So far this year the company says it has taken orders on 50-, 60- and 74-metre yachts – €200m worth of boat – as well as letters of intent on several more. The company has no intention of expanding into the market for "ultra-mega yachts" of the type recently purchased by the Chelsea owner Roman Abramovich, whose 160-metre Eclipse is the world's biggest, featuring two helipads and a submersible escape submarine.

But the client base is changing. A tripling in the number of super-yacht owners in Singapore in four years has meant a series of uniquely Asian challenges for shipbuilders to meet, including demands to turn them into floating karaoke lounges.

"Five hundred years ago, a thousand years ago, the rich men, the noblemen, they would build giant castles," says Mr Tacoli. "Yachts, they are the castles of their era.

"The Russian market has expanded, and the Asian too. There are new billionaires in these places, but not all billionaires want to buy yachts. Brazil, India China, they have money but they don't have the yachting culture to go with it yet. A yacht is a purchase for someone with a certain type of mentality. They want to go have fun on them. They want to show off. The Indian clients, the Chinese, they prefer to use them as a second home, or for hosting business meetings."

They might have the money, it seems, but they don't have Monte Carlo, they don't have Sardinia, Florida or the Caribbean. These places are the natural home of yachts, at least for the time being.

"The culture is improving in China, but they still don't have the marinas, the infrastructure of elsewhere. There has always been Hong Kong. Now there is Hainan too. Soon there will be more.

"There is potential in Brazil, China and India. In 10 years' time they may be the real buyers, they will have more of the people rich enough to buy them. But will they have the yachting culture to go with it? We don't know."

In the meantime, if, like Derek Trotter, this time next year you think that you might be a billionaire, then you will have to act quickly. The next available delivery date is already 2015. One minor problem exists: the 10 per cent deposit up-front.

World's biggest toys – and the big boys who own them

1. 'Eclipse'

557ft

Roman Abramovich

Features a missile-detection system and a laser shield to hinder the paparazzi's cameras. It also holds the distinction of being the world's largest, compensating perhaps for the owner's lack of soccer success this year.

2. 'Dubai'

532ft

Sheikh Mohammed bin Rashid Al Maktoum

This floating palace has seven decks, with jacuzzis and a mosaic swimming pool. It can also support a nine-tonne helicopter.

3. 'Al Said'

508ft

Qaboos bin Said al Said

The Sultan of Oman's yacht has a helipad, a cinema and a concert hall which can accommodate a 50-strong orchestra.

4. 'Prince Abdulaziz'

482ft

Saudi Royal Family

The world's largest and most expensive yacht when it was built in 1984. Its luxurious lobby was inspired by that of the doomed Titanic ocean liner

5. 'El Horriya'

478ft

Egypt Presidential yacht

Built in Britain in 1865 and originally owned by King of Egypt. Later became a Naval training vessel. Most recently owned by deposed leader Hosni Mubarak.