The female water spirits Yawk Yawk or Ngalkunburriyaymi are perhaps the most enigmatic of mythological themes. Sometimes compared to the European notion of mermaids, they exist as spiritual beings living in freshwater streams and rock pools, particularly those in stone country. The spirit Yawk Yawk is usually described and depicted with the tail of a fish. Thus the Kuninjku people sometimes call them ngalberddenj which literally means 'the young woman who has a tail like a fish'. They have long hair, which is associated with trailing blooms of green algae (called man-bak in Kuninjku). At times they leave their aquatic homes to walk about on dry land, particularly at night.