Picture of Contact with Sea Urchin
The effect of contact with a sea urchin. Sea urchins are a gastronomic delight when prepared properly, but a cutaneous torture when stepped on unprepared. The echinoids have spines that in some species are several inches long. Driven into skin when one steps or falls on or brushes against the creatures, the hard spines break and lodge in skin. Pain is inevitable, and secondary infection is nearly inevitable if they are left in. Nothing but tedious and meticulous extraction of every one of dozens, possibly scores, of spines is required for relief.
Text: WebMD Medical Reference