Can anyone identify this macroalgae?

[Cthulukelele]

It started growing on my rock recently. Any ideas?

 

[Cthulukelele]

Here is a pic with less blue

 

[Subsea]

Where did the rock come from? If you had said Gulf of Mexico, I would guess Halimeda Elongata.

https://www.marineplantbook.com/marinebookhalymeniaelongata.htm

Or

https://www.marineplantbook.com/marinebooknemastoma.htm