Any Idea Why My Hammer Has a Bubble?

[Waffen06]

Noticed at night my hammer has a huge bubble on the right side/bottom?

 

[Vette67]

I don’t know about what you’re seeing, but I have a plate coral that has a very similar bubble on it. This has been on my plate coral for at least 6 months. So it has not been fatal and the coral is otherwise seemingly fine.

 

[Waffen06]

I went and circled it, its a clear bubble