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

• Austria's Migaloo is offering to build a private "submersible superyacht" for the ultrarich.
• It says the M5 would be able to travel 820 feet underwater and stay submerged for a month.
• Despite the high up-front cost, CEO Christian Gumpold says the firm is in talks with 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 would 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 Business Insider, adding: "These wishes do not just include performance, length, or design."

Gumpold said that yacht owners were "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 could be designed around any customer priority, whether that's security, thrill seeking, research, or simply vacation.

The company offers prospective buyers a checklist of options, 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 could feasibly host a wealth of supplemental vehicles, including mini submarines, exploration vehicles, and working boats, it said.

Although at times it's described in the company marketing materials as a "private submersible superyacht" the M5 would technically be able to sail as a submarine — an underwater vessel that can launch itself and return under its own power, rather than having to be launched by a mother ship.

It's envisioned as being able to house up to 20 guests and about 40 staffers.

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

The most expensive megayachts ever sold now run into the half-billion-dollar 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 had 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 like science fiction, addressing problems that would either apply only to the ultrarich or which the rest of us would be too dead to care about.

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

That's on top of a gamut of features that any megayacht owner might 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 depended on the scope of the client's requests, comparing it to the price tag on large superyachts.

According to Fast Company's estimation, there are only 50 people in the world who could 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 was "still in close contact with several potential owners worldwide" and "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 awhile before any of them would take to the seas.