Blue stuff growing on my rock

[SeeDemTails]

I looked at my LR today up close and found some navy blue stuff groing on the rock.

Here is a pic...The color is off due to the crappy macro on my camera(always buy canon), but it is more of a navy blue.

Is this a type of coraline?

 

[austinsdad]

Some kinda sponge maybe?

 

[Devilishturtles]

Some kinda sponge maybe?

Sure looks like an encrusting sponge to me as well.

 

[SeeDemTails]

Good or bad?

 

[Fluff]

It's neither good or bad, it just "is". I wouldn't worry about it. Most sponges are harmless and do no more than filter your water for you.