What could this be?

[carried]

This appeared on my rock a few days ago. It's soft and has a white base and a bright green top. I haven't seen any tentacles coming out of it. Could it be some kind of sponge? Thanks for the help

 

[AquaRick]

Looks like a tunicate. Is it more fleshy or does it have perforated points like a sponge?

 

[carried]

Looks like a tunicate. Is it more fleshy or does it have perforated points like a sponge?

I think it's more fleshy and it doesn't appear to have perforated points.