EAGLE-EYED BEACHCOMBERS may recognise the round white shells etched with a five-petal flower. These erstwhile homes of sea urchins resemble a silver dollar, earning them the nickname “sand dollars” and the myth that they are the money of mermaids or the long-lost city of Atlantis. They pile up on the shores of the 700 islands in the Bahamas, so its central bank picked the sand dollar as its logo. In October 2020, when the Bahamas launched the world’s first central-bank digital currency (CBDC), the authorities chose to adorn the app with the familiar floral pattern and call it the sand dollar.