Visible. Wikipedia As the number of people visiting the sea in the summer increases, there is another creature to watch out for in addition to jellyfish. This is a spiny urchin that can be commonly seen in crevices of rocks or around breakwaters. It looks like an ordinary sea urchin on the outside, but if you accidentally step on it, the long thorns can get stuck deep into the soles of your feet and cause pain for several days. The problem is not the poison, but the thorns that break. Spiny crabs have black or dark purple bodies...