What is this, is it a tunicate?

[Keith Schaab]

I was looking at this, it kind of looks like a sponge but it looks more like a mollusc to me and it seems to be moving across the rock (slowly). Never seen anything like it; is it some type of tunicate (do they move positionally)? The spikes open almost like coral polyps.

A little more zoomed in:

 

[ISpeakForTheSeas]

Welcome to Reef2Reef!

That appears to be a Gold Ring Cowrie, Monetaria annulus. These are reportedly reef-safe and good CUC.

 

[Keith Schaab]

Thanks, definitely seems like you're right!