British architect Norman Foster was relaxing on a friend’s yacht in the Mediterranean when he noticed a school of dolphins playing in the boat’s wake. That would be a great shape for a superyacht, he said.

That was five years ago. Fast-forward to 2010 and an industrial boatyard in La Spezia, Italy's chief naval port, is putting the finishing touches to the unlikely project. With its great stretches of industrial power and petroleum plants, La Spezia is not a place one might associate with the glamorous world of superyachts. But the Rodriguez Cantieri Navali boatyard was singled out by Foster in 2005 to build a fleet of four identical, 41m yachts that he would sell shares of through YachtPlus, the fractional ownership company for which he designs.