From a distance, Tatsuro Yokoi looks like a pirate clinging to the mast of a sunken galleon.

Move closer — sorry, make that swim closer — and you notice he lacks the eye patch, the parrot on the shoulder and the hook for a hand. You also notice that he is actually moving at a fair clip and is standing on what looks like a small, semisubmerged airplane with its short wings angled down into the water like a shark’s side fins.

Did somebody say “shark”? You don’t want to do that — not when you’re swimming 100 meters from the Zushi shoreline in Kanagawa Prefecture chasing a product- designer-turned-inventor as he tests out the latest version of the one-man waterborne vessel he’s named the Swing Roll Flipper.

The “swing roll” in the name of Yokoi’s contraption, which he first made in 2005 but has been tinkering with ever since, provides a hint as to how it is propelled. Standing atop what would be the “fuselage” if this really was a small plane, the rider gently rocks the craft from left to right. With each swaying movement, the winglike fin on one side moves up through the water while the one on the opposite side moves down. That way, forward thrust is generated. Waist-high handlebars help the rider to maintain balance and stay on board.

“Once you get the hang of it, it’s easy,” Yokoi calls out as he cuts a wide arc around his journalist pursuer, who by now has acquired the use of a kayak. Yokoi once worked for Sony. “It’s long,” he warned when asked the name of the section to which he belonged — nonetheless obliging with an answer that translates as “Dynamic Image Marketing Enterprises Section.”

Apparently he was making 3-D and interactive video entertainment 25 years before James Cameron. “But our section wasn’t really concerned with whether a product could be commercialized,” he added with a giggle.

Come the early 1990s, and Yokoi started to notice more and more computers being moved into his company’s studios — and more and more drawing boards being moved out. It was then that he decided his allegiances lay with the latter, so he threw in the corporate towel to pursue his own low-tech projects.

But what had been good enough for Sony continued to be good enough for Yokoi. Few of his inventions over the last 18 years have been made with commercial viabiity in mind. Last week, for instance, he tested out a pointy hatlike device that turns its backstoke-swimming wearer into something akin to a torpedo, albeit one with flailing arms and legs.

Fortunately, he has been able to supplement his income with revenue from a windsurfer-storage facility — aptly named Mercy’s — that he operates on his property near the beach at Zushi. “It’s the same place where I grew up,” he said.

One invention that Yokoi did feel the need to patent was a three-hulled craft resembling three windsurfer boards linked into a V-shaped formation with one ahead and two behind to the sides. U.S. Patent 5,682,831, dated Nov. 4, 1997, says that Yokoi’s invention allows the crew to keep at least one of the craft’s flat-bottomed hulls “parallel against the water surface regardless of the heel of the boat . . . thereby decreas(ing) water resistance.”

Nevertheless, the invention hasn’t been put into commercial production.

It was experimenting with the trimaran that made Yokoi aware of the potential of a finned boat. In its drawing-board stage, the Swing Roll Flipper actually resembled a whale, with a single horizontal fin at the back. The problem was how to make the whale kick, as no human operator could be expected to raise and lower the “tailfin” for sustained periods.

That’s where the idea of wings rocking up and down on each side came in — enabling a rider to generate power simply by shifting their own body weight alternately to the left and right.

The first prototype was fashioned entirely from wood. Later versions — including the current two — use “fuselages” made of more easy to shape Styrofoam (wrapped in either fiber-reinforced plastic or a lacquered synthetic material). The fins and other fittings, meanwhile, are made from wood or plastic — “whatever I can get my hands on,” Yokoi said.

The designer is currently awaiting the outcome of his application for a U.S. patent for the craft. It’s difficult to predict the ease of riding a machine you’ve only just set eyes on. When I rode a Segway (see JT, Nov. 15, 2009), I came away thinking it was much easier than it looked. The Swing Roll Flipper, I have to say, was very much the opposite.

Sure, you just sway it back and forth, but overdo it and one fin comes out of the water. And when that happens, there’s little you can do to stop the whole thing turning turtle. Short sways in quick succession are what are required, as I discovered after several tries. Keep that in mind and you can generate enough speed to easily outrun a rowboat.

The most difficult thing for a sunken Swing Roll Flipper pirate to do is remount his vessel in deep water. Like a tightrope walker returning from a seated pose to a standing one, Yokoi was able to leap into his footholds and balance himself at the same time. By the time I got to the balancing bit, it was all too late — I was treading water and trying not to think about those sharks again. I soon retreated to my waiting kayak.

Between laughs, Yokoi promised that “improving stability” would promptly be added to his must-do list. Also, by making adjustments to the flexibility and shape of the wings, he hopes to bump up the top speed from 7 or 8 to about 11 kph.

And, last of all, he hopes to find friends having sufficiently agile minds and bodies to share his passion. Those interested in walking on water are advised to keep close watch on the sea off Zushi.

Check out video footage of Tatsuro Yokoi riding on his Swing Roll Flipper earlier this month at search.japantimes.co.jp/cgi-bin/fl20100620x2.html His Web site is at sports.geocities.jp/srflipper61

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