What is "marimo"

Aegagropila linnaei, known as in Japanese and as Cladophora ball, Lake ball, Mossimo or Moss Balls in English, is a species of filamentous green algae ( Chlorophyta) found mostly in a number of lakes in the northern hemisphere. A marimo is a rare growth form of the species where the algae grow into large green balls with a velvety appearance. Colonies of such balls are only known to form in Iceland, Scotland, Japan, Estonia and, in 2014, Australia.