One of the surest signs of Spring in Boston -- aside from Opening Day in Fenway Park -- is the yearly return of the Swan Boats. Adding a fairy tale element to the heart of the city, the world-famous boats have navigated the 3-foot deep lagoon in Boston’s renowned Public Garden since 1877. In that entire time, they have been owned and operated by a single dedicated family, the Pagets. Over a hundred years ago, Robert Paget was inspired by seeing Richard Wagner’s opera, Lohengrin, in which the title character rescues his heroine, Princess Elsa, in a boat drawn by a swan. Despite their graceful and fanciful appearance, each boat weighs an un-swan-like three tons. Pedaling the boats is hardly an effortless task for crewmembers, but their work is greatly appreciated. Since the picturesque boats first came to the Lagoon, they have been enjoyed by residents and tourists alike, and have been the setting for many a romantic proposal.