Underwater superyachts? A CEO is pitching fantastical ships that can go 800ft down and stay submerged for weeks.

• Austria-based Migaloo is offering to build luxury submersible yachts for the ultra-rich.
• It says the M5 will be able to travel 820 feet underwater and stay submerged for a month.
• Despite the high upfront cost, CEO Christian Gumpold says they're in talks with multiple buyers.

Forget megayachts. Forget billionaire basements. If you're unfathomably rich and want a new toy, there's an Austrian company that says it will build you a fully submersible yacht.

And this is no rickety Titan submersible.

The Migaloo M5 concept, the company says, involves a 540-foot base model superyacht that can travel about 820 feet underwater and stay down there for up to a month.

"The needs of superyacht owners for their vessels are more complex than ever," Migaloo CEO Christian Gumpold told BI, adding: "These wishes do not just include performance, length, or design."

Gumpold said that yacht owners are "looking for privacy, security and protection for themselves, their guests and their valuables, or for the fulfillment of unique experiences up to scientific desires as well as for the greatest possible exclusivity."

According to its marketing materials, Migaloo says the vessel's layout and features can be designed around whatever priorities the customer has, whether that's security, thrill-seeking, research, or simply vacation.

The company offers potential buyers a checklist of possible features, including LED exterior lighting with a laser show, a helipad, a hot air balloon, and — for the aspiring Bond villain — an underwater shark feeding station.

The vessel can potentially host a wealth of supplemental vehicles, including mini-submarines, exploration vehicles, and working boats, it said.

It's envisioned as being able to house up to 20 guests and around 40 staff.

The Migaloo concept clearly aims to cater to an increasing desire for privacy and security among the world's richest people.

The most expensive megayachts ever sold now run into the half-a-billion-dollars range or more, with at least three $600 million yachts afloat, owned by various oligarchs and oil-state royalty.

Bobbing about underwater in a Migaloo M5, Elon Musk wouldn't have to worry about a jet-tracking student any longer.

Gumpold told BI he has specialized in yacht design since 2008, and he promised that all the complex arrangements of the Migaloo project — working with shipyards, flag states, and classification societies — would be taken care of by his company.

Much of the marketing material for Migaloo runs to possibilities that sound science fictional, addressing problems that will either only ever apply to the ultra-rich, or which the rest of us will be too dead to care about.

Saying it works with security company SAFE, Migaloo claims it can create a "private submersible fortress," offering protection from EMP pulses, cybercrime, piracy, solar flares, asteroids, and polar shifts.

That's on top of a gamut of features that any megayacht owner might feasibly expect, including spas, gyms, a gaming room, a wine cellar, an art gallery, and a panic room.

The cost, however, is the ultimate "if you have to ask, you can't afford it" test.

Gumpold told Fast Company that the price depends on the scope of what the client asks for, comparing it to the price ticket on large superyachts, which can run into hundreds of millions of dollars.

According to Fast Company's estimation, there are only 50 people in the world who can afford to purchase a luxury submergible megayacht.

It remains to be seen if and when any prospective buyers will bite.

Gumpold told BI his company is "still in close contact with several potential owners worldwide" and is "very close" to executing the first project steps.

But he didn't elaborate on any concrete steps and wouldn't name any of his prospective clients.

With a turnaround time of about four to seven years, it's also going to be a while before any of them take to the seas.