James Bond would look at home in one of these machines.
Personal submarines are the latest must-have accessories for wealthy yacht owners looking for exciting ways to enjoy the water.
A decade ago, so-called "submersibles" were rarely found outside scientific and military circles but private use has spiked over the past few years. The market has grown alongside the jump in wealth for the top 1%, and a drop in the average age of millionaires.
"The younger, more adventurous owners want more out of their yacht than just sitting on the back drinking a cocktail," said Graham Hawkes, founder of luxury sub maker DeepFlight.
DeepFlight makes two-person submersibles that resemble underwater jets. They cost at least $1.5 million and can typically dive to around 120 meters, or what founder Hawkes describes as the edge of darkness.
Clients, who include entrepreneur Richard Branson and venture capitalist Tom Perkins, are chasing unique encounters with ocean life in comfort and safety. Hawkes recalls coming face to face with a Great White shark while teaching Branson to "fly" the submarine.
"We were gobsmacked," Hawkes said. "That 30 seconds was worth everything, the 20 years of effort. It was just awe inspiring."
The machines are custom made but DeepFlight is considering moving to regular production runs as the market grows. In the last few years the company has sold 2 or 3 each year, and this could rise as high as 10, according to Hawkes.
Triton Submarines is another firm benefiting from growing demand: Chief executive Bruce Jones said the company has more orders than ever. At $3.5 million, the Triton 3300/3 is the company's most popular model. This sub carries 3 people and dives to around 1,000 meters.
"It's quite an unusual experience to go down deep in a submersible, [so owners] are heroes with their family and friends," Jones said.
But before shelling out for a personal submarine you'd really have to own a superyacht to berth it on. Superyachts cost hundreds of millions of dollars, and the smallest are about the size of a tennis court. Some are four times as big. With that in mind, Jones said a typical Triton client would be worth around $500 million.
Those who can scrape the cash together could soon find themselves behind the wheel of a luxury sub. DeepFlight and Triton offer pilot training but there's no specific license required.
"Nobody buys the a Ferrari to give the keys to a chauffeur," Deepflight's Hawkes said.