Bill Joy, co-founder of Sun Microsystems, is building a $50 million yacht — an eco-friendly 190-footer named Ethereal — to be the most efficient, eco-friendly boat afloat.

Joy, who is now a venture capitalist at Silicon Valley venture firm Kleiner Perkins Caufield & Byers, apparently told Fortune (flip through the glossy pages here; you’ll have to go to page 82 for the full thing) he wants it to be an ambassador for the “green tech” he and his new firm are championing. Pesky light-bulbs, for example, will be designed to use as little light as possible. Lithium-ion batteries will be used for lower, steadier power.

His yachtsman is New Zealander Ron Holland. This should give you some incentive to work hard and make some cash. It’s part of a trend. More and more newly-minted millionaires are building yachts, the article says.