What is this? Coral, hitch hicker?

[Fatjim]

I noticed this on my rock about 2 days ago, it hasn't moved at all but is awfully suspicious.
It almost looks like hammer bubbles but I have no clue how it could pop up where it is.
I have 2 hammers side by side, I know that they can split to make new heads but have never heard of them breaking off to spread.

I'd love any input

 

[Fatjim]

Pics

 

[Fatjim]

My only other guess is snail eggs, which I have nassurous (4) bumblebee bee (4) astrea (2) turbo (1) stomatella (5+)

 

[Hreef]

I have BumbleBee Snails, I’m guessing these are their eggs?
Thanks