When it comes to building giant superyachts, the ocean's the limit.
The world's mega-rich are ordering ever larger boats and Middle East buyers are helping to drive a recovery in this market for the ultimate status symbol in the wake of the financial crisis.
The biggest yacht to date, the 180-metre Azzam, was completed by the German shipyard Lürssen this year and exceeds some commercial cruiseliners in size. According to media reports, Azzam was built for an estimated €500 million (Dh2.45 billion).
It has knocked the 163-metre Eclipse, owned by the Russian billionaire Roman Abramovich and reportedly equipped with a missile defence system and a submarine, into second place. Eclipse is believed to have two swimming pools, one of which can be converted into a dance floor.
But even the mighty Azzam, due to be delivered later this year and capable of top speeds exceeding 30 knots, is likely to lose its title soon.
Industry insiders say someone plans to order a private yacht soon that will exceed 200 metres.
Renowned designers such as Donald Starkey have produced such a 200 metre yacht concept. Berkeley March, another yacht architect, told CNN in 2010 that his concept 200m boat could cost up to Dh3.67bn to build, "depending on the needs of the clients".
According to Mr March, the yacht, known only as "Project 1000", could be in the water by 2015.
The plans, drawn up for Emocean Yacht Design based in Belgium, call for a drive-in garage, two 30-metre day boats, a helipad with a hangar, 10 VIP suites and 22 guest suites.
Superyachts are generally defined as being at least 30 metres long. The market is expanding along with the size of the boats and Abu Dhabi investors have been positioning themselves by purchasing whole shipyards in Europe in recent years to secure expertise and tap into a growth market.
Abu Dhabi Mar owns the French firm Constructions Mécaniques de Normandie (CMN) and Germany's Nobiskrug and also has a stake in the civilian shipbuilding operations of Germany's Howaldtswerke-Deutsche Werft, giving it a broad portfolio that comprises not only yachts but commercial and naval ships as well.
"The boat-buying populace is being led now by the Middle Eastern people, by the Russians and the Americans," says Russell Crump, the yacht sales director at Yachting Partners International, a yacht brokerage house.
"We're seeing green shoots in the economy and that has spurred people on to say maybe this is the time to buy because as these green shoots get bigger the prices will start getting higher and higher."
"2013 is not the best year ever but I would describe it as buoyant and I think momentum in the market-place will carry on," he adds.
"I think any savvy brokerage house is going to be looking forward to the next three years with a lot of optimism."
The current global fleet of superyachts amounts to 4,181 boats, according to Boat International, a superyacht magazine. Last year, there were 488 such yachts under construction worldwide, and so far this year there are 469 yachts being built.
As the average size of the vessels is increasing, the gross tonnage of yachts is also growing year by year. When Boat International began compiling its list of the world's top 100 largest yachts in 1990, the smallest was 45 metres long. Now the smallest is at 77 metres. At present, there are 27 superyachts more than 100 metres in length and 19 more in construction. In 1983, there were just five.
A yacht of 100 metres or more will set you back at least €200m. And the running costs can amount to some €2m per year.
The mega-wealthy could have afforded to buy new yachts throughout the crisis but with the world pulling out of the downturn, they now feel freer to engage in conspicuous consumption on such a scale again.
"I don't think any of the money at the top end went away but I think a lot of people either had priorities elsewhere and were focused on their businesses or they did not want to be seen to be spending the money when they were having to lay off workers at their companies, perhaps," says Mr Thomas.
"It's not the best image to project. But gradually we're coming out of that and predictions are that the brokerage market has been pretty strong this year, as strong as any year since 2008."
Most yachts more than 80 metres long these days have helicopter landing pads as a standard feature. Two or three-seater submarines are becoming increasingly popular.
"If you want to build the best superyacht ever you can do what you like because you've got all the space in the world," says Mr Crump.
"Provided you've got the money, any designer and any shipbuilder will have the time and the ideas. You can do absolutely anything. I heard the other week that someone's putting a seaplane on their yacht." Marine architects are also developing new designs for tenders - the smaller boats used for ferrying people to and from the yachts.
"I think on the larger yachts we'll see clever ideas for tender launching and getting in and out of the tender, it can become quite difficult in the big sea. We might see some funky tenders come out or lot of tenders, one fast one, one passenger one," says Mr Crump.
The bigger the yachts become, the more important the tenders, because many of the most exclusive jetset resorts are too small to offer berths for the new giants. If the owners and passengers want to avoid commercial ports, which are not the most romantic or attractive locations, they will need to anchor out at sea and use tenders to reach trendy harbours such as St Tropez in France or Porto Cervo in Sardinia.
But many new yachts offer their own on-board seafront experience. New designs permit the stern to be folded down to form a platform on the water.
"You can have a big beach club and a swimming pool down there, with a sauna and massage and steam rooms," says Mr Thomas.
"The idea of a big beach club cum spa area is becoming very popular.
"Traditionally on older boats you'd have technical space or a tender garage at the rear but now they're being moved elsewhere," he says.
"You end up with an amazing guest area, they can sit there and sunbathe by the water rather than being cooped up at the top of the yacht."
At some point, the quest for ever bigger yachts is likely to come to its natural conclusion, say analysts.
"The amount of volume you have with anything over 100 metres is so big that it becomes very impersonal, you just end up with a lot of boat that never gets used," says Mr Thomas.
German yards such as the family-owned Lürssen, HDW, Blohm und Voss and Abeking & Rasmussen are the market leaders for superyachts but Dutch rivals are scaling up their production capacities. Italian companies such as Fincantieri are also in the market but at the smaller end.
China has also started building superyachts but its yards still lack the reputation to attract many buyers.
"The respect isn't there for Chinese yachts," says Mr Crump.
"If you're a discerning billionaire, you go and buy a Lürssen or a Blohm und Voss or a Fincantieri because you can afford to do it. To be frank, if you're buying a 100-metre boat for €200m, it doesn't matter whether it costs €200m or €250m, you might as well have the brand behind it."
It is a market Abu Dhabi, home to the yacht builder ADMShipyards, is keen to expand in.
Mr Crump says he believes Abu Dhabi investors are currently in negotiations with some of the biggest shipyards in Europe.
"A lot of expertise goes into building a shipyard, to get it right you need the expertise and that has been growing in Germany and Holland and Europe, so you've got to bring those guys in and they're expensive.
"Rather than building in the Middle East and bringing all the technology there, it makes sense to keep the technology where it is, keep the brains where they are, and own it."