Purple sea urchins sit in the depressions they’ve carved over time into the tide pool, minimizing the force of the waves as the tide comes in and out. I came across these urchins in 2004 on a sunny day at Yaquina Head Outstanding Natural Area in Newport, Oregon. The picture below is a different set of urchins but taken on the same day, I’ve posted this one before but it was years ago.
Boolie 