Performed my daily inspection and in doing so I found this unreformed seen creature..

[Reef.ductionist]

Ditto... At first I thought it was some sort of leather but checked back ten minutes later and saw it had moved from the top of the rock to the sand...looks like some kind of sea urchin but not sure...
anyone seen these guys before?

It's the round green thing at the base of the rock.
Cheers.

 

[Rob.D]

I'm stumped.

 

[Reef.ductionist]

Few more pics/
Maybe a sea Apple?

The above pic is from the right
The below pic is from the left side

 

[iretthepirate]

Looks like a sponge from what i can tell