The world of hyper-luxury is filled with outrageous products, from $300,000 watches that don't tell time to $6 million floating islands and shadow yachts.
But summertime seems to bring out a rash of "fantasy" products for the super-rich—crazy trophy toys that are either too crazy or cutting-edge even for today's super-rich.
Here are three of this summer's best fantasy toys for billionaires. While none has been built or sold yet, they should be—if purely as entertainment for the rest of us.
1. The Submarine Yacht. Cruising above the water is so yesterday. Today's thrill-seeking rich want a deeper experience when it comes to the open seas. Hence, the submarine yacht. Motion Code: Blue, an Austrian design firm, has come up with the "Migaloo," a 377-foot submarine that has all the amenities of a yacht—including a pool, sun deck and massive staterooms —but can also reach a depth of 240 meters underwater.
The company says guests on the ship can "travel amongst a school of whales heading into the deep while having a cup of tea and a good chat in the main saloon."
The vessel has eight VIP suites, a library, gym, gaming room and a cinema room—for those moments when watching migrating blue whales and giant squid from the sub windows becomes overly tiresome.
A spokesman told the Daily Mail that the vessel is "the result of intense research and the firm's excellent knowledge of the current yacht market."
Price tag: undisclosed.
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2. PRIVATE JUMBO JET. Private jets are getting bigger and bigger. But none can compare to the "VIP A-380," a pimped-out version of the hulking A-380 super-jumbo. Saudi Prince Alwaleed bin Talal bought an A-380 to outfit as a private jet but before the jet was completed, it was sold to another user. It's unclear whether the new buyer is a company or person, and whether it will be used for personal or commercial purposes.
Still, the designer Edese Doret created a special design for Alwaleed's plane, called the "Flying Palace," which was never built. It featured a 14-seat dining table, a glass chandelier, and a "magic carpet room" that has a transparent floor to see the views below. Alas, the whirlpool tub never made the final cut for the design.
Theoretical price tag: $500 million.
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3. LAND YACHT. The world of luxury mash-ups— submarine-yachts, mansions in the sky—wouldn't be complete without a land yacht. Rest assured, the folks at Marchi Mobile brings us the "eleMMent Palazzo"—a 45-foot bulbous giant of a recreational vehicle that includes heated floors, a massive master suite, a rainshower and loads of marble. It's also got a roof-top terrace and driver's seat cockpit that's more like a jumbo-jet cockpit.
Price: $3 million.
—By CNBC's Robert Frank. Follow him on Twitter @robtfrank.