Rangiroa, FP 'ball-like' object ID needed???.....What is it??.......

[diver 85]

Have 2 shots of it----don't remember the size or depth pic was taken..........TIA........

IMG_9817 by GEAUXtiger, on Flickr

IMG_9816 by GEAUXtiger, on Flickr

 

[scooky]

I was there about 6 weeks ago. I think they guide said it was a type of Urchin.
Not confident in that though.

 

[Cali_diver]

Cushion Sea Star, Culcita novaeguineae

 

[chillyinCanada]

+1 for Calidiver's answer