Barnacle Billie really working the coral on her carapace out in the burbs. Working on her right side in image below:

And then her left side:

You can see a tpoby at the top of her neck. It kept working her neck and shey would quickly lift or side throw

her head to get it off. In the pic below she just lifted her head straight up to clear it away.

Some video segments taken from above of her working her carapace against the coral: