For those who have everything: The Seabreacher X

The Seabreacher X is a personal watercraft like no other. This 17-foot-long, two-seat submersible can hit 50 mph on flat water or cruise just below the surface—and even launch itself into the air like a flying fish. A digital camera/periscope on the dorsal fin lets you keep an eye on the world above when you’re down below.
From $81,000, seabreacher.com
Source: Popular Science