For the Man who has Everything: A Private Submarine

And this is no scrunched-up little submersible like your science geek uses to look for new species around sea floor vents. No, this is underwater cruising with style:

Clearly, the Phoenix provides its owner with substantially more capability than a simple yacht - the opportunity to explore the depths of the world's oceans in perfect comfort and safety. The Phoenix is capable of making trans-Atlantic crossings at 16 knots yet can dive along the route and explore the continental margins of some of the most fascinating waters on earth. And unlike surface yachts, when the water gets rough, the submarine can submerge into a perfectly smooth and quiet environment, continuing on toward its destination, providing a ride unsurpassed in quality-unequaled by the finest motor coach or the most luxurious executive aircraft.

At 65-meters (213 feet) in overall length, and with a beam in excess of 8 meters (26 feet), the Phoenix is a vehicle of formidable size. Yet despite its 1500-ton displacement, the submarine is quite streamlined. Given the significant waterplane area and ample internal volume, which allows for greater battery storage, the Phoenix will out-perform smaller counterparts in surface speed, submerged speed and submerged endurance. The large pressure hull diameter allows for very large acrylic viewports, making the undersea viewing capability truly extraordinary. The interior space, with the noted absence of structural bulkheads, provides for tremendous versatility in interior layout and space planning. And finally, the Phoenix's large size coupled with its integrated roll stabilization system makes surface transit quite comfortable in all but the worst conditions.

The Phoenix can dive to 305 m (1000 feet) and stay submerged for 360 hours. Could be yours for a mere $78 million. And if that is too pricey for you, U.S. Submarines offers three smaller but still luxurious submersible yachts.

Or how about this sporty two-person model from Triton Submarines, capable of diving to 1000 meters (3300 feet)? The brochure calls this the "sexiest deep submersible" in the world.

And if that's still too tame, you could go for the Triton 36000 FOD --Full Ocean Depth --which will take you to the bottom of the Marianas Trench in just 75 minutes.

Truly there has never been a better time to be a billionaire.