(CNN) - Most of us will never set foot on a swanky superyacht. We'd be lucky to even catch a glimpse of one of these streamlined, gleaming vessels docked in Monaco or Miami.
But for billionaires in the top 1% wealth bracket, a superyacht is a must-have sign of status -- and the perfect way to travel the world.
Luxury yachts have been sailing the seas since the early 20th century. Since then, designs have got bigger, better, more extravagant and more adventurous.
So where next for these opulent ocean-goers?
CNN Travel recently weighed anchor at the Superyachts Top 100 symposium in London to discover the major superyacht trends to watch out for in 2019 and beyond.
The most obvious direction for the next generation of elite seagoing vessels is an increase in size -- more and more are now exceeding the 100-meter mark and heading for supersize status, says Jonathan Beckett, CEO of superyacht brokerage Burgess.
Currently, Superyachts Top 100 ranks a boat launched in 2013 as the world's longest. Azzam, measuring 180 meters end-to-end, was built by German shipyard Lurssen and is now belived to be owned by United Arab Emirates President Khalifa bin Zayed al-Nahyan.
Once 40-meter boats were considered modest compared with larger craft; now even 60-meter vessels are seen as small by today's standards, Beckett explains.
This rise in the number of larger yachts is directly linked to an increase in the number of billionaires, says a representative of Dutch shipbuilders Feadship.
Plus, thanks to the booming tech industry, billionaires are getting younger. These millennial magnates want bigger boats, in more unusual designs that challenge expectations.
They're still the preserve of the wealthiest of the wealthy though. As one symposium attendee puts it, for a vessel of 120 meters or more "you need to be a sheikh or an oligarch."
Younger yacht owners aren't, apparently, interested in a white yacht with a spotless exterior and the traditional "wedding cake" shape.
Instead, these junior billionaires want their floating palaces to double up as genuine ocean-going sea craft, capable of reaching far-flung corners like Alaska, the Northwest Passage and beyond.
This is where "explorer" yachts come in -- state-of-the-art vessels that, while perhaps less glamorous, have the capacity to chart more extreme waters.
"A Land Rover of the sea, instead of a Bentley," is how British yacht designers H2 describe this new breed of upscale boat.
Among them is REV Ocean -- currently being built by Norwegian company Vard. With a projected length of 182.6 meters, it's the largest superyacht currently under construction.
When built, it'll steal the world's largest superyacht accolade from Azzam -- assuming no other upcoming yachts go even bigger.
REV Ocean is being created to match the specific vision of its owner, Kjell Inge Røkke.
Røkke is a billionaire Norwegian businessman who, after owning several more conventional superyachts, decided he wanted something different: an explorer vessel that could provide both personal pleasure and contribute to improving the state of the world's oceans.
Due to launch in 2020, REV Ocean will have a Scandi industrial chic luxury interior equipped with a lecture theater, submarines and laboratories.
Its exterior will be equipped for adventure.
"[The owner] brainstormed with a few designers and technicians and thought -- maybe we could split the boat into two, in a way, and have a luxury part of it but also have it as a functioning research vessel," Lawrence Hislop, communication manager for REV Ocean, tells CNN Travel.
"It's one thing to sail on top of the ocean, but there's so much technology available now that lets you get underneath the water and explore the oceans in a completely unique way," says Hislop.
REV Ocean isn't the first of its kind, although its arguably taking the concept to new heights.
The explorer-style superyacht has been floating around for some time, with Microsoft co-founder Paul Allen's 126-meter Octopus vessel starting the trend back in 2003.
But it's now becoming more common.
While superyacht manufacturers agree that more and more clients want to voyage beyond the traditional blue-water havens of the Mediterranean and Caribbean, those chartering private yachts seem less inclined to go exploring in less benign seas.
But for those with the cash to own a personal yacht, the ability to get away from the crowds is increasingly paramount.
Explorer or not, crazily extravagant features continue to be de-rigueur on the superyacht circuit.
The Russian preference is for a snow room -- an icy spa chamber complete with tumbling flakes. US clients want a gym. Helicopter pads are normal.
On Feadship's Faith, a 96-meter superyacht which made its maiden voyage in 2017, a curved-glass swimming pool forms the watery backdrop to the downstairs bar.
Other features include stabilized pool tables (or even dining tables that convert to pool tables) and aquariums. High-spec IMAX cinema projection equipment is also in demand alongside lower-tech popcorn machines.
Italian superyacht company Bennetti highlights gimbaled wine cellars -- which keep the floor level against ocean undulations so as not to disturb the expensive vintages stowed on board.
Stabilization to prevent drink glasses from wobbling is also a thing, as is noise-reduction, but these mechanical extras come at a high price.
Something like a gold tap, for example, is expensive not necessarily because of the gold, but because of the mechanism involved, says a spokesman for German shipbuilders Lurssen.
More play, less work
Another trend is exterior and interior design that allows yacht guests to get as close as possible to the water.
Whereas the prime real estate on a superyacht was once the sundeck, now a "beach club" area closer to the water is more desirable, says H2.
This trend is seen in most yachts that have premiered in the past couple of years. A prime example is Italian yacht builder Fincantieri's design for upcoming vessel Private Bay, a 120-meter vessel, equipped with a luxurious beach club, al fresco cinema and sea-level pool.
Yacht designers seek to emphasize the connection with the ocean in other ways too.
Another upcoming Fincantieri yacht, Mirage, reflects water with its glass panels, giving the 106-meter vessel the illusion of blending seamlessly into the sea.
In the past wealthy tycoons often used their superyachts to conduct important business matters, but Dutch yacht builder Oceanco says there's been a move away from this with fewer request for offices on board as owners prefer to use them as places to relax with family.
It's linked to a desire for privacy, says Oceanco's representative at the symposium. He points out that owners use the yacht for shorter, more frequent vacations.
Instead of offices, owners want spas, gyms, pools and cinema rooms -- features that appeal more to their kids than prospective business partners.
Steering an enormous boat across the world's oceans is never going to be a particularly eco-friendly affair -- but all the companies involved in the London symposium agree that owners are becoming increasingly concerned with the environmental impact of their yachts.
This quest for low-emission sailing is leading to new innovations in design, such as Oceanco's Black Pearl, delivered in 2018.
This imposing sailing yacht is over 106 meters long, with three incredible black sails made from carbon fiber by Dykstra Naval Architects.
The yacht's 2,900 square meters of sails can be set in seven minutes, via the push of a button.
The Black Pearl aims to be the most fuel-efficient superyacht ever, capable of traversing the Atlantic without burning any fuel -- although it will come equipped with a hybrid diesel-electric system.
The Black Pearl's owner -- reportedly Russian billionaire Oleg Burlakev, co-founder of oil and gas company Burneftegaz -- says he's been inspired to acquire the boat as much by environmental awareness as by an interest in innovation due to their engineering background.
"Eco-consciousness is vital for the future of our planet," the owner said, in a statement provided by Oceanco. "I wholeheartedly support research that will drive us to more sustainability and I have ensured that green technology was very much a part of the creation of Black Pearl."
The Black Pearl won a prize for Best Naval Architecture for Sailing Yachts in the 2019 Boat International Design & Innovation Awards -- although its design remains in flux. Oceanco are also hoping to refit the yacht with solar sails in the future.
Nobiskrug's Sailing Yacht A, believed to be owned by another Russian billionaire, Andrey Melnichenko, also draws power from hybrid sources. The company says it hopes such technology will become as common in yachts as it is in road vehicles nowadays.
Like Black Pearl, Sailing Yacht A has three masts, but unlike the newer yacht, she's not fully fuel-free and instead operates as a sail-assisted motor yacht.
The yacht is almost 143 meters in length with 10-meter masts made of carbon fiber. Her unusual height meant that air traffic had to be suspended when she recently sailed past Copenhagen.
There's even an elevator on the masts, just for fun. Brave guests can ascend to the top and admire views to the horizon.
Nobiskrug's spokesman says that superyacht owners are willing to pay more for greener vessels, but the yachts are never going to be fully emission-free. All the ships have air conditioning, for example.
Plus, some superyacht owners are going to be more interested in pushing the boat out (pardon the pun) on eco-innovation than others.
Feadship's spokesman adds: "Ultimately, it's the whims of the client."
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