Large, segmented worms that frequently reached a length of 300 meters or more, they were responsible for the production of the spice melange on Arrakis. The conversion of carbon dioxide to oxygen took place during this process, eliminating Arraiks' need for plants. Drowning a young sandworm produced the Water of Life, used in Bene Gesserit rituals and in the selection of the Kwitzatz Haderach.
The Fremen used them as really impressive tanks.