Parisian haute couture designers have been diving deep for inspiration this season—literally. Jean Paul Gaultier, like Karl Lagerfeld at Chanel, plunged into an aquatic adventure, though in his case, it was "Little Mermaid says, 'Hello Sailor!' " You can always count on JPG for a fun tableau to get things started, so there she was: Coco Rocha, posing on a rock against a watery backdrop with soap bubbles floating up around her.

The mergirl-mariner theme made a neat excuse for another of Gaultier's signature cross-gender mergers. It opened with a couple of memorably chic twists on Parisian classics: a stunning slim navy coat over a striped sweater and sinuous gold-sequin column skirt and a semitranslucent scallop-edged trench that might have been made of fish skin. From there, he trawled the oceans for similes: macramé made to look like fishing nets, plissé inserts suggesting underwater flora, chiffon fronds floating like seaweed, cascading paillettes imitating fish scales or mother-of-pearl, necklaces fashioned into spongiform beads.

It ended with Rocha, making an entrance as the mermaid bride on coral crutches, with a pair of conical shells for a bra. That was a typical ta-da Gaultier punch line, and the couturier was certainly in a cheery mood afterward. "When I started couture, I really thought couture customers were dead or dying," he said. "But now there are all these new clients. We're working all the time, and I love it—it's a permit to create!"