I cant see nothing in picture it to blurry.but images of aiptasia below.
Has it got a round mouth?
Tentacles around edge?
Retracts back into rock if touched?
Everyone will need better picture im thinking, but you best to see as what you can see we cannot.
Look up aiptasia,feather dusters,majano anemone/tube worms.
These all can look similar if not seen before.