Even in retirement, Burt Rutan keeps working, and the legendary aeronautics designer is up to something cool.

When Rutan retired to Idaho in 2011 after a lifetime designing revolutionary airplanes, he dreamed of flying around the world with his wife, Tonya—but soon realized that if he wanted an airplane capable of making the trip the way he imagined it, he'd have to design it himself. He's spent the past few years in his garage, creating an airplane capable of landing on rough seas, calm lakes, snow, or grass. It also runs on gasoline instead of aviation fuel.

"Imagine an aircraft able to land in large swells near any ocean shoreline and ride the waves to the beach, from where you could hike in for lunch and gas," Rutan said in a statement AnntennaFilms released Thursday. "Since it uses car/boat gas … it will rarely go to an airport. Imagine also going to snow fields anywhere there is around 400 feet of relatively smooth snow, or to a dirt patch right at Puma Punku, or any part of the Amazon, including the tiny rivers that feed it. Imagine doing an eight-month exploration trip around the world without EVER going to an airport. I know it sounds like Walter Mitty, but if it flies well, Tonya and I will explore the world with it, visiting the places you cannot easily get to any other way."

Burt and Tonya Rutan Archive

Rutan always has been secretive about his designs until they are ready to fly, and he won’t release any details about this aircraft until after its first flight, which might be by this summer. But to support AntennaFilms, which is making a crowdfunded documentary film about his life and work, Rutan agreed to release the few teasing details about the amphibious plane, which he calls the SkiGull.

The SkiGull, with its skis extended, will be able to land in rough seas or on calm lakes and rivers. The skis also incorporate small wheels that will enable it to land on runways and fields. With the skis retracted, the airplane can perform belly landings on smooth water, like other seaplanes. Although seating will be limited to Rutan and his wife, the plane will have cavernous fuel capacity – Rutan wants to be able to fly from California to Hawaii without carrying supplemental ferry tanks. He's aiming for a cruise speed of 170 knots (195 mph).

This isn't he first time Rutan, age 71, has shaken things up. The brilliant aerospace designer is famous for unusual ideas and innovative designs. He popularized the use of composites and canards in home-built aircraft; he designed Voyager, the first airplane to fly around the world nonstop; and he built the spaceship that won the $10 million Ansari X Prize and became the basis for Virgin Galactic’s commercial spacecraft. But his greatest legacy may well be Scaled Composites, the Mojave, California company he founded in 1982. It has trained and influenced two generations of designers, engineers, and aviators.

The SkiGull may be Rutan’s last airplane, capping an amazing career while letting him explore the world, without limits, to write the final chapter of his life.