I tried. This isn't a very good video, but you can kinda see it's still trying to crawl away after it's been eaten at several points. I might have had 20 or so in a pile fresh out of the water and they were much more active. I hope this helps.

I like the fat ones. The long ones don't taste good.

It’s true! I would collect them in a pail from the tidal pools as a child. I would crack them open with whatever I had available and eat them, and the halves would still be running around on the ground after I discarded the rest.

The parts of urchin, the remains, they would skitter around and bunch up in one corner of the yard trying to get away like they didn’t realize they’d been eaten yet even though there was nothing left inside.