A sand dollar is a type of sea urchin. Many are flat, but others that are more rounded are called sea biscuits. Sand dollars are related to starfish and sea cucumbers. Sand dollars are often found together on the ocean floor or seabed. They eat small sea creatures, algae, and the remains of animals that reach the ocean floor. Sand dollars have spines, and thus, have few natural predators.


In the ocean, sand dollars can be a variety of colors including brown, green, blue, and purple. People usually see them when they wash up on the sand. By this time, they are often broken and bleached white by the sun. The sand dollar got its name for its resemblance to a silver dollar when found on the sand.