Definitely not an acro crab. 90% sure its not a decorator crab. I only saw it for 10 seconds, then Benny the Blade spooked it back in the rock. Really freaky. It was gone in a blink. I believe it was coaxed out with some arcti pods.
I can't seem to find anything online like this, looks like a spider, much larger than the Zoa eating kind. Lived through my dip procedure apparently. I'd say he could stretch across a quarter easily. Moved like lightning.
Thanks