Live sand dollars range in color from gray to purple to deep red, and one side of the body is lighter than the other. They vary in size and are flattened discs resembling sea urchins. Sand dollars lie flat when in the water and stand vertically when it comes time to eat.
Sand dollars are related to sea cucumbers, starfish and sea urchins. They have tubular feet and soft spines called cilia, which help them collect food. The sand dollars found on the beach are dead and turned white due to the sun's bleaching effect.
Sand dollars have their mouths on the bottom of their bodies and they breathe through pores located on their endoskeletons.