Web like growth in rocks. Ideas?

[Steve1500]

I just found this growing in my rocks. Only in one location and it’s where my damsels (3 azures) hangout. It almost looks like a nest of some sort but I am concerned it is something else. It has tiny holes and is semi transparent. I don’t see any eggs but it’s not transparent enough to see inside. Any ideas?

 

[nereefpat]

The white in the center? Looks like a sponge from here.