The small sand crabs of the family Scopimera and Dotilla of the family Dotillidae live on the tropical beaches of the Pacific Ocean and the Indian Ocean. Their carapace measures only about one centimeter across, so you will almost miss them when you look at it. But you will most likely see the results of their work at the time of tide.
These animals live on microscopic biological material, called detritus. They can only reach it at a time when the sea level is falling and the sand is sufficiently damp.
At that moment crabs will crawl out of their underground dungeons and begin to find food. At an incredible speed, they squeeze a grain of sand into their mouths, filtering edible pieces of detrity. The sand forms into small balls, which slowly sink around their nests and create remarkable patterns. When the tide arrives, the crabs will come again and their waterwork will flush their filigree work.