A sea urchin is a small, spiny marine animal found on ocean floors around the world. They have a round, hard shell called a test, covered in sharp spines that help protect them from predators. Sea urchins are often found in rocky areas and are known for their unique ability to move slowly using tiny tube feet. These creatures play an important role in their ecosystems by grazing on algae, which helps maintain the balance of underwater plant life. Some people enjoy eating sea urchin, especially the edible part known as uni, which is considered a delicacy in many cuisines, including Japanese and Mediterranean.