To board the yacht named Christina, in the glamorous late middle of the 20th century, was to float amid the highest levels of fame, celebrity and royalty: Winston Churchill! Liza Minnelli! Rudolf Nureyev! Its owner, the Greek shipping magnate and definitive international playboy Aristotle Onassis, equipped it with a lapis lazuli fireplace, an onyx spiral staircase, a swimming pool with a mosaic bottom that ascended to become a dance floor, and barstools upholstered in whale-penis leather.