At the ocean’s edge, the crash of waves against the shore is a familiar sound. It might be rhythmic, but it’s not particularly melodious. There are, however, a few spots around the world where the tides, waves and wind make actual music, thanks to acoustic man-made structures that use the movements of seawater to produce sound. Currently, three of these so-called tidal organs have been built, one each in Croatia, England and the United States.