As the superrich try ever harder to impress each other, submarines are the next frontier, and personal luxury subs are all the rage right now, where the undersea boats are approaching the size of cruise ships with all the amenities you could imagine.
For example, U.S. Submarines offers the Phoenix 1000, a 213-foot personal luxury submarine that was originally custom-built for a client but is now for sale at an undisclosed price. There's 5000 feet of living space, with huge viewports on the side. It's capable of transoceanic crossings, and when the weather gets rough, the boat can submerge into a perfectly smooth and quiet environment. Take a look at the company's site, where there's a variety of submarines from which to choose. Wow.