Elegant Biwa freshwater Pearl necklace with Mother of Pearl pendant Length approximately 17 inches. Biwa pearls are unusually shaped cultured pearls from the freshwater mussels of Lake Biwa, Japan. In 1914, pearl farmers began growing cultured freshwater pearls using the pearl mussels native to Lake Biwa. This lake, the largest and most ancient in Japan, lies near the city of Kyoto.