Graham Hawkes calls his products functional luxurious. As he explains it, they are “the same as a Ferrari but not a Rolls-Royce”—in other words, built for speed and not comfort.

But the two-seaters Hawkes makes are for cruising sea depths, not scenic routes. His San-Francisco-based company, Deep Flight Submersibles, started in the 1970s by building tiny submarines that allowed researchers to inspect the ocean floor. In the past three years, however, a demand for private minisubs has surfaced, as more people have been buying mega-yachts and stocking them with mega-toys like seaplanes, Jet Skis, kayaks, and speedboats.

No one knows just how many personal submarines are out there—the Coast Guard, incidentally, simply considers them boats—but anecdotal evidence suggests they have become more popular with nautical nabobs. And why not? If you feel like you’ve seen the world’s most comely coastlines and ravishing reefs, you can use a minisub to explore shipwrecks and spend time on the bottom of the sea.

“You’ve got unlimited access to the depths of the ocean,” says Mark Ragan, who gives lessons in his yellow (a popular color) two-person, 14-foot-long K-250 sub in Annapolis, Maryland. “You have the ability to dive whenever you feel like it without getting wet. At anchor in your yacht in the Caribbean, you just get in and go night diving.”

Today’s submarines can go faster and deeper than their predecessors, and they are easier to control than the Lotus Esprit S1 submarine car that James Bond steered in The Spy Who Loved Me. They can be as simple as a $18,000 homebuilt sub, or as elaborate as the immense underwater yachts that go for tens of millions of dollars.

Each sub, like the Wright brothers’ flying machines, is a one-off creation. One example is the $1.5 million, two-person Super Falcon, which Deep Flight started building in July for venture capital guru Tom Perkins. (Its name is derived from Perkins’ yacht, Maltese Falcon, which the sub will accompany.) By the time it’s delivered in May, the Super Falcon will have a modern fighter jet’s controls and be just as maneuverable. Its state-of-the-art electronics will project an artificial horizon along with speed, depth, and navigational information onto the canopy. “It’s all very familiar to anybody who flies an airplane,” Hawkes says.

Of course, that’s the Ferrari. The Rolls-Royce of personal subs is something like U.S. Submarines’ Phoenix 1000. The Phoenix is 213 feet long—compared with 252 feet for an early German U-boat—and can cruise at 16 knots underwater. (The vintage U-boat could do only 7.) It can cross the Atlantic submerged (so you can avoid the weather and still enjoy the view), and it’s infinitely more luxurious than a warship, with 5,000 square feet of living space, five staterooms, ports that offer a broad view, and common areas packed to the gills with leather and wood furnishings, all custom designed to the owner’s specifications. This submarine can even be equipped with its own sub, a two- to eight-person mini capable of diving up to 2,000 feet—or even functioning as an escape vehicle. The Phoenix price: $78 million.