Mystery Lunch?

This huge sea urchin was one of several up on the rocks by my favourite swimming spot. It raised a few questions....
How did it get there?
Was it washed up there?
Surely it would have been smashed up?
Did a seagull get it?
If so how did a seagull get it?
They live quite deep under water don't they?
Or maybe it was a cormorant?
Is that what they are diving for?
How do they bring it up on the rocks however they get it off the seabed?

It is a mystery! All of the ones on the rocks were as big, and had similar 'smashed' holes.....