You have the private plane, the luxury yacht and the helicopter. Only one high-tech goody is missing from the list of billionaire playthings - a deep-water submarine.
But thanks to a revolution in ultra-strong materials and advanced guidance systems, such a super-submersible is being built, and sold, by marine companies.
Soon the abyss, and the strange denizens that inhabit its stygian depths, will be filled with packs of tiny submarines piloted by hedge-fund managers and venture capitalists.
Among those who have shown keen interest, either in funding or buying super-submersibles, are film director James Cameron, Google executive chairman Eric Schmidt and entrepreneur Richard Branson.
"Ninety per cent of the seabed has still to be explored," said Patrick Lahey, president of Triton Submarines of Vero Beach, Florida. "There is a host of wonders down there. You could visit the mid-Atlantic thermal vents, where volcanic heated gases bubble up from Earth's core, or cruise down to the wrecks of the Titanic or the Bismarck. You will be able to access any place in the ocean and watch all those wonderful sea creatures."