What is this?

[Azul17]

I found this under one of my rocks. Anyone knows what this is?

Is slimy and looks like the tentacles on a bubble tip but they are open. Also it’s transparent and has no color. On top of the rock I have some zoas.

 

[Sniperhank]

Looks like some type of tunicate to me, if you're saying that they have an open end on them. If not and are closed I'd say bubble algae.