Sea urchins are something kids in Hawaii (at least this kid) grow up semi-dreading--step on one and your beach day is over. But as an adult, I've come to appreciate those tasty little buggers. They are pure, briny goodness...as raw oysters are, but more concentrated.
(Top image of sea urchin in Hawaii waters via HornetBear. Bottom photo of sea urchin and other fishy lovelies, Honolulu, Hawaii).