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.