Sea urchins don’t have eyes, so they use their feet to see. Tucked among their spines are little holes. Inside the holes are tentacle-like things called “tube feet.” The tube feet have light-sensitive cells at their base. Researchers think the sea urchin’s whole body acts like a giant eyeball. Urchins don’t see very well, but their “foot-sight” is good enough to guide them toward shelter or groups of other sea urchins for safety.